JP2014063955A - Polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing method which can form a smooth vertical plane on an edge part of a wafer.SOLUTION: A polishing method of the present invention comprises: a first polishing process for pressing a polishing tape 38 against the edge part of a wafer W with a pressuring pad 51 to polish the edge part of the wafer W in a state where a part of the polishing tape 38 is protruded toward inside of the wafer W in a radial direction from the pressuring pad 51 after rotating the wafer W, and folding a part of the polishing tape 38 along the pressuring pad 51; and a second polishing process for polishing the edge part of the wafer W more with the polishing tape 38 by pressing a part of the polishing tape 38 that has been folded, toward inside of the wafer W in a radial direction with the pressuring pad 51.

Description

  The present invention relates to a polishing method for polishing a substrate such as a wafer, and more particularly to a polishing method for polishing a peripheral portion by pressing a polishing tape against the peripheral portion of the substrate.

  In order to polish a peripheral portion of a wafer, a polishing apparatus provided with a polishing tool such as a polishing tape or fixed abrasive is used. This type of polishing apparatus polishes the peripheral portion of the wafer by bringing the polishing tool into contact with the peripheral portion of the wafer while rotating the wafer. In this specification, the peripheral portion of the wafer is defined as a region including a bevel portion located on the outermost periphery of the wafer and a top edge portion and a bottom edge portion located on the radially inner side of the bevel portion.

  36 (a) and 36 (b) are enlarged cross-sectional views showing the peripheral edge of the wafer. More specifically, FIG. 36A is a cross-sectional view of a so-called straight type wafer, and FIG. 36B is a cross-sectional view of a so-called round type wafer. In the wafer W of FIG. 36 (a), the bevel portion includes an upper inclined portion (upper bevel portion) P, a lower inclined portion (lower bevel portion) Q, and a side portion (apex) R. This is the outermost peripheral surface (indicated by reference sign B). In the wafer W of FIG. 36B, the bevel portion is a portion (indicated by reference numeral B) that forms the outermost peripheral surface of the wafer W and has a curved cross section. The top edge portion is a flat portion E1 that is located on the radially inner side of the bevel portion B. The bottom edge portion is a flat portion E2 located on the opposite side of the top edge portion and located radially inward of the bevel portion B. Hereinafter, the top edge portion E1 and the bottom edge portion E2 are collectively referred to as an edge portion. The edge portion may include a region where a device is formed.

  In a manufacturing process of an SOI (Silicon on Insulator) substrate or the like, it is required to form a vertical plane and a horizontal plane at the edge portion of the wafer W as shown in FIG. Such a cross-sectional shape of the edge portion is achieved by a polishing method as shown in FIG. That is, the edge portion of the wafer W is polished by pressing the edge portion of the polishing tape 301 against the edge portion with the pressing pad 300 while rotating the wafer W. The lower surface of the polishing tape 301 constitutes a polishing surface holding abrasive grains, and this polishing surface is arranged in parallel with the wafer W. Then, by pressing the polishing surface of the polishing tape 301 against the edge portion of the wafer W with the pressing pad 300 in a state where the edge portion of the polishing tape 301 is positioned at the edge portion of the wafer W, as shown in FIG. , A perpendicular cross-sectional shape, that is, a vertical plane and a horizontal plane can be formed at the edge portion of the wafer W.

  However, since the vertical surface is formed by scraping the edge portion of the wafer W with the edge portion of the polishing tape 301, the vertical surface may become rough as shown in FIG. Further, as shown in FIGS. 39B to 39D, the shape of the vertical surface may change before and after the replacement of the pressing pad 300 which is a consumable item.

  In the manufacturing process of an SOI substrate or the like, it may be preferable to form a reverse tapered surface as shown in FIG. 40 instead of the vertical surface shown in FIG. However, it is difficult to form such a reverse tapered surface by the polishing method shown in FIG.

JP 2011-224680 A JP 2011-171647 A

Accordingly, a first object of the present invention is to provide a polishing method capable of forming a smooth vertical surface on an edge portion of a substrate such as a wafer.
A second object of the present invention is to provide a polishing method capable of forming an inversely tapered surface on an edge portion of a substrate such as a wafer.

  In order to achieve the above-described object, according to a first aspect of the present invention, the pressing pad is rotated in a state where a part of the polishing tape protrudes radially inward from the pressing pad. The polishing tape is pressed against the edge portion of the substrate to polish the edge portion of the substrate, and the first polishing step of bending the part of the polishing tape along the pressing pad is performed and bent. Performing a second polishing step of further polishing the edge portion of the substrate with the polishing tape by pressing the part of the polishing tape toward the inner side in the radial direction of the substrate with the pressing pad. Polishing method.

In a preferred aspect of the present invention, the part of the bent polishing tape is longer than the depth of the portion to be polished formed on the edge portion of the substrate by the first polishing step.
In a preferred aspect of the present invention, at least one of the first polishing step and the second polishing step is performed while moving the polishing tape in the longitudinal direction.
In a preferred aspect of the present invention, the moving direction of the polishing tape opposes the traveling direction of the edge portion of the rotating substrate.
In a preferred aspect of the present invention, the polishing tape in the first polishing step is a coarse polishing tape, and in the second polishing step, a fine polishing tape is used instead of the coarse polishing tape. It is characterized by being used.

  According to a second aspect of the present invention, in the state where the substrate is rotated and a part of the polishing tape protrudes radially inward of the substrate from the pressing pad, the polishing tape is moved to the edge of the substrate by the pressing pad. A first polishing step is performed in which the edge portion of the substrate is polished by being pressed against a portion, and after the first polishing step, a part of the polishing tape is pressed against the edge portion of the substrate. By bending the portion of the polishing tape bent along the pressing pad toward the inside in the radial direction of the substrate by the pressing pad, thereby further pressing the edge portion of the substrate with the polishing tape. A polishing method characterized by performing a second polishing step for polishing.

In a preferred aspect of the present invention, at least one of the first polishing step and the second polishing step is performed while moving the polishing tape in the longitudinal direction.
In a preferred aspect of the present invention, the moving direction of the polishing tape opposes the traveling direction of the edge portion of the rotating substrate.

  According to a third aspect of the present invention, in the state where the substrate is rotated and a part of the first polishing tape protrudes from the first pressing pad toward the inside in the radial direction of the substrate, The first polishing step is performed by pressing the first polishing tape against the edge portion of the substrate to polish the edge portion of the substrate, and a part of the second polishing tape is transferred from the second pressing pad to the substrate. The second polishing tape and the second pressing pad are positioned so as to protrude inward in the radial direction of the substrate, and the part of the second polishing tape is moved to the substrate by the first polishing step. The second polishing pad is pressed against the corner portion formed on the edge portion of the second polishing pad by the second pressing pad, and the part of the second polishing tape is bent along the second pressing pad. The portion of the tape is transferred to the second By pushing toward the radially inner side of the substrate by pressure pad, a polishing method which comprises carrying out the second polishing step of further polishing the edge portion of the substrate at the second polishing tape.

  In a preferred aspect of the present invention, an end portion of the second pressing pad is located radially outside a vertical surface formed on the edge portion by the first polishing step, and the second pressing pad is The positioning of the second polishing tape and the second pressing pad is performed such that the horizontal distance between the end portion and the vertical surface is larger than the thickness of the second polishing tape. And

In a preferred aspect of the present invention, the first abrasive tape is a coarse abrasive tape, and the second abrasive tape is a fine abrasive tape.
In a preferred aspect of the present invention, the first polishing step is performed while moving the first polishing tape in the longitudinal direction.
In a preferred aspect of the present invention, the moving direction of the first polishing tape opposes the traveling direction of the edge portion of the rotating substrate.
In a preferred aspect of the present invention, the second polishing step is performed while moving the second polishing tape in the longitudinal direction.
In a preferred aspect of the present invention, the moving direction of the second polishing tape opposes the traveling direction of the edge portion of the rotating substrate.

  According to a fourth aspect of the present invention, while rotating the substrate and pressing the polishing tape against the edge portion of the substrate with the pressing pad, the polishing tape and the pressing pad are moved inward in the radial direction of the substrate. Polishing, characterized in that a slide polishing step is performed until the stop position is reached, the slide polishing step is repeated, and each time the slide polishing step is performed, the stop position is moved slightly inward in the radial direction. Is the method.

According to the first to third aspects of the present invention, the vertical surface can be formed on the edge portion of the substrate by the first polishing process, and the vertical surface can be smoothed by the second polishing process.
According to the fourth aspect of the present invention, an inversely tapered surface as shown in FIG. 40 can be formed on the edge portion of the substrate.

It is a mimetic diagram for explaining a polish device for carrying out one embodiment of a polish method concerning the present invention. FIG. 2 is a plan view of the polishing apparatus shown in FIG. 1. FIG. 3A to FIG. 3D are views for explaining an embodiment of the polishing method according to the present invention. It is a figure for demonstrating other embodiment of the grinding | polishing method which concerns on this invention. It is a figure for demonstrating the other example of the grinding | polishing method shown in FIG. It is a schematic diagram which shows the grinding | polishing apparatus provided with the 1st grinding | polishing unit and the 2nd grinding | polishing unit. It is a figure explaining the method of grind | polishing a wafer using the grinding | polishing apparatus shown in FIG. It is a figure for demonstrating other embodiment of the grinding | polishing method which concerns on this invention. It is a figure for demonstrating the manufacturing process of an SOI substrate. It is a figure for demonstrating other embodiment of the grinding | polishing method which concerns on this invention. It is a top view which shows a grinding | polishing apparatus. It is the FF sectional view taken on the line of FIG. It is the figure seen from the direction shown by the arrow G of FIG. It is a top view of a polishing head and a polishing tape supply and recovery mechanism. It is a front view of a polishing head and a polishing tape supply and recovery mechanism. It is the HH sectional view taken on the line shown in FIG. FIG. 16 is a side view of the polishing tape supply / recovery mechanism shown in FIG. 15. FIG. 16 is a longitudinal sectional view of the polishing head shown in FIG. 15 viewed from a direction indicated by an arrow I. It is the figure which looked at the position sensor and the dog from the top. It is a figure which shows the grinding | polishing head and the grinding | polishing tape supply collection mechanism which were moved to the predetermined grinding | polishing position. 3A to 3D are schematic views of the pressing pad, the polishing tape, and the wafer at the polishing position when the polishing method shown in FIGS. 3A to 3D and the polishing method shown in FIGS. It is. It is a figure which shows the state which has pressed the polishing tape against the wafer with the press pad. It is the schematic diagram which looked at the press pad, polishing tape, and wafer when implementing the grinding | polishing method shown in FIG. FIG. 24A to FIG. 24C are diagrams illustrating the operation when detecting the edge of the polishing tape. FIG. 25A is a view of the polishing tape and the pressing pad in the polishing position as viewed from the radial direction of the wafer, and FIG. 25B is a state where the lower surface of the pressing pad is in contact with the upper surface of the polishing tape. FIG. 25C is a diagram illustrating a state where the pressing pad presses the polishing tape against the wafer from above. FIG. 26A is a view showing a state where the wafer is bent as a result of pressing the polishing tape against the wafer with the pressing pad, and FIG. 26B is polished in the state shown in FIG. It is sectional drawing of a wafer. It is a longitudinal cross-sectional view which shows the wafer holding part provided with the support stage. It is a perspective view of a support stage. It is a figure which shows the state which the holding stage and the wafer hold | maintained on the upper surface raised relatively with respect to the support stage. It is a figure which shows embodiment provided with the tape stopper. It is a figure which shows the state which the abrasive tape received and received the load of the horizontal direction. It is a figure which shows embodiment with which the tape stopper and the tape cover were provided. It is a figure which shows embodiment provided with the movement restriction | limiting mechanism which restrict | limits the outward movement of a press pad. It is a figure which shows the example which combined embodiment shown in FIG. 27 and embodiment shown in FIG. It is a top view which shows the grinding | polishing apparatus provided with the some grinding | polishing unit. 36 (a) and 36 (b) are enlarged cross-sectional views showing the peripheral edge of the wafer. It is a figure which shows the vertical surface and horizontal surface which were formed in the edge part of a wafer. It is a figure for demonstrating the grinding | polishing method for forming the vertical surface and horizontal surface which are shown in FIG. 39 (a) to 39 (d) are enlarged views showing a cross section of the edge portion of the wafer polished by the conventional polishing method. It is sectional drawing which shows the reverse taper surface formed in the edge part of a wafer.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic view for explaining a polishing apparatus for carrying out an embodiment of a polishing method according to the present invention, and FIG. 2 is a plan view of the polishing apparatus shown in FIG. The polishing apparatus includes a wafer holding unit 3 that holds and rotates a wafer W that is a substrate, and a polishing unit 25 that polishes an edge portion of the wafer W held by the wafer holding unit 3.

  The polishing unit 25 includes a polishing tape support mechanism 70 that supports the polishing tape 38, a pressing pad 51 that presses the polishing tape 38 against the edge portion of the wafer W, and a vertical that moves the pressing pad 51 in a direction perpendicular to the wafer surface. A moving mechanism 59, a radial moving mechanism 45 that moves the pressing pad 51 and the vertical moving mechanism 59 in the radial direction of the wafer W, and a tape moving mechanism that moves the polishing tape 38 and the polishing tape supporting mechanism 70 in the radial direction of the wafer W. 46.

  The radial direction moving mechanism 45 and the tape moving mechanism 46 can operate independently of each other. Therefore, the relative position between the pressing pad 51 and the polishing tape 38 in the radial direction of the wafer W can be adjusted by the radial movement mechanism 45 and the tape movement mechanism 46. As the vertical movement mechanism 59, the radial direction movement mechanism 45, and the tape movement mechanism 46, a combination of air cylinders or a combination of a servo motor and a ball screw can be used.

  The polishing tape 38 is supported by the polishing tape support mechanism 70 so that the polishing surface thereof is parallel to the surface of the wafer W and the polishing surface faces the edge portion of the wafer W. One surface (lower surface) of the polishing tape 38 constitutes a polishing surface to which abrasive grains are fixed. The polishing tape 38 is a long polishing tool and is disposed along the tangential direction of the wafer W. The pressing pad 51 is a pressing member for pressing the polishing tape 38 against the edge portion of the wafer W, and is disposed above the edge portion of the wafer W. A tape stopper 185 that restricts the horizontal movement of the polishing tape 38 is fixed to the bottom surface of the pressing pad 51. This tape stopper 185 may be omitted.

  FIG. 3A to FIG. 3D are views showing an embodiment of a polishing method according to the present invention. As shown in FIG. 3A, a part of the polishing tape 38 (a part extending in the longitudinal direction of the polishing tape 38) protrudes from the pressing pad 51 toward the inside in the radial direction of the wafer W. And the pressing pad 51 are positioned. In this state, as shown in FIG. 3B, the pressing pad 51 is pushed down by the vertical movement mechanism 59 to press the polishing surface of the polishing tape 38 against the edge portion of the rotating wafer W. By further pressing down the pressing pad 51, the edge portion of the wafer W is polished until a vertical surface and a horizontal surface are formed on the edge portion of the wafer W as shown in FIG. 3C (first polishing step). The wafer pressing surface of the pressing pad 51 is a horizontal plane parallel to the wafer surface, and a vertical surface and a horizontal plane are formed on the edge portion of the wafer W by pressing the polishing tape 38 against the edge portion of the wafer W with this horizontal pressing surface. . The polishing surface of the polishing tape 38 that is in contact with the wafer W is parallel to the surface of the wafer W. The inner edge of the pressing pad 51 during polishing is pressed against the edge of the wafer W via the polishing tape 38.

  As the pressing pad 51 moves downward, a part (protruding portion) of the polishing tape 38 protruding from the pressing pad 51 is bent upward along the pressing pad 51. In this state, as shown in FIG. 3D, the vertical surface is polished by the bent portion of the polishing tape 38 by pressing the pressing pad 51 toward the inner side in the radial direction of the wafer W by the radial movement mechanism 45. (Second polishing step). When the polishing tape 38 is bent, the polishing surface comes into contact with the vertical surface of the wafer edge portion. Accordingly, the vertical surface of the wafer W is polished by the polishing surface of the polishing tape 38.

  Thus, the vertical surface formed on the edge portion of the wafer W in the first polishing process is polished by the polishing surface of the polishing tape 38 in the second polishing process. Therefore, the vertical surface can be smoothed. In the first polishing step, a coarse polishing tape for rough polishing may be used, and in the second polishing step, a fine polishing tape for final polishing may be used. As shown in FIG. 3C, it is preferable that a part of the bent polishing tape 38 is longer than the depth of the portion to be polished formed on the edge portion of the wafer W (that is, the height of the vertical surface). .

  If the polishing tape 38 is simply pressed against the edge portion of the wafer W during polishing, polishing marks may remain on the edge portion. In order to solve this problem, at least one of the first polishing step and the second polishing step may be performed while moving the polishing tape 38 in the longitudinal direction. By polishing while feeding the polishing tape 38 in this way, polishing marks formed on the wafer W can be removed. In this case, in order to increase the polishing rate of the wafer W and to make a geometrically correct shape, it is preferable that the moving direction of the polishing tape 38 opposes the traveling direction of the edge portion of the rotating wafer W. In order to more effectively remove polishing marks, it is preferable to move the polishing tape 38 in the radial direction of the wafer W while pressing the polishing tape 38 against the edge portion of the wafer W.

  FIG. 4 is a view for explaining a polishing method according to another embodiment of the present invention. Since the configuration and operation of the present embodiment that are not particularly described are the same as those of the above-described embodiment, a duplicate description thereof is omitted. In step 1, the polishing tape 38 and the pressing pad 51 are formed such that a part of the polishing tape 38 (portion extending in the longitudinal direction of the polishing tape 38) slightly protrudes from the pressing pad 51 toward the inside in the radial direction of the wafer W. Is positioned. This positioning is achieved by the radial movement mechanism 45 and the tape movement mechanism 46. The polishing tape 38 is located above the edge portion of the wafer W. The reason why a part of the polishing tape 38 protrudes from the pressing pad 51 is to prevent the pressing pad 51 from coming into contact with the edge portion of the wafer W during polishing of the wafer W.

  In step 2, the pressing pad 51 is pushed down by the vertical moving mechanism 59 to press the polishing surface of the polishing tape 38 against the edge portion of the rotating wafer W, thereby forming a vertical surface and a horizontal surface on the edge portion of the wafer W (first polishing step). ). The inner edge of the pressing pad 51 during polishing is pressed against the edge of the wafer W via the polishing tape 38. In step 3, the pressing pad 51 and the polishing tape 38 are raised by the vertical movement mechanism 59, and the polishing tape 38 is separated from the wafer W.

  In step 4, the pressing pad 51 and the polishing tape 38 move by a predetermined distance toward the inside in the radial direction of the wafer W while being separated from the wafer W. More specifically, the inner edge of the polishing tape 38 is located radially inside the vertical surface of the wafer W, and the inner edge of the pressing pad 51 is located radially outside the vertical surface of the wafer W. Until then, the pressing pad 51 and the polishing tape 38 move in the radially inner direction of the wafer W. The movement of the pressing pad 51 and the polishing tape 38 in Step 4 is achieved by the radial movement mechanism 45 and the tape movement mechanism 46.

  In step 5, the pressing pad 51 and the polishing tape 38 are lowered by the vertical movement mechanism 59. The width of the protruding portion of the polishing tape 38 in step 5 may be the same as or larger than the width of the protruding portion in step 1. In step 6, a part (projecting part) of the polishing tape 38 is pressed against a corner where the vertical surface and the surface (upper surface) of the wafer W intersect to bend a part of the polishing tape 38 upward. This corner is formed at the edge of the wafer W by the first polishing process. In step 7, the vertical surface is polished by the bent portion of the polishing tape 38 by pressing the pressing pad 51 inward in the radial direction of the wafer W by the radial direction moving mechanism 45 (second polishing step). When the polishing tape 38 is bent, the polishing surface comes into contact with the vertical surface of the wafer edge portion. Accordingly, the vertical surface of the wafer W is polished by the polishing surface of the polishing tape 38.

  Also in this embodiment, the vertical surface formed on the edge portion of the wafer W in the first polishing process is polished by the polishing tape 38 in the second polishing process. Therefore, a smooth vertical surface can be formed on the edge portion of the wafer W. At least one of the first polishing step and the second polishing step may be performed while moving the polishing tape 38 in the longitudinal direction. In this case, in order to increase the polishing rate of the wafer W, it is preferable that the moving direction of the polishing tape 38 opposes the traveling direction of the edge portion of the rotating wafer W. Furthermore, it is preferable to move the polishing tape 38 in the radial direction of the wafer W while pressing the polishing tape 38 against the edge portion of the wafer W in order to remove polishing marks.

  In Step 3 and Step 4 shown in FIG. 4, the polishing tape 38 is once separated from the wafer W, but even if a part of the polishing tape 38 is bent while the polishing tape 38 is in contact with the edge portion of the wafer W, Good. This example will be described with reference to FIG. FIG. 5 is a view for explaining another example of the polishing method shown in FIG. The first polishing process shown in Step 1 and Step 2 is the same as Step 1 and Step 2 shown in FIG. After the first polishing process, in Step 3, with the polishing tape 38 in contact with the wafer W, the pressing pad 51 and the polishing tape 38 are moved inward in the radial direction of the wafer W, and a part of the polishing tape 38 (projecting) Part) is pressed against the vertical surface of the edge formed in the first polishing step, and a part of the polishing tape 38 is bent upward. In step 4, the vertical surface is polished by the bent portion of the polishing tape 38 by further pressing the pressing pad 51 inward in the radial direction of the wafer W by the radial direction moving mechanism 45 (second polishing step).

  The first polishing step (steps 1 to 3) and the second polishing step (steps 4 to 7) shown in FIG. 4 may be performed using different types of polishing tapes. In this case, as shown in FIG. 6, a polishing apparatus including a first polishing unit 25A and a second polishing unit 25B having the same configuration is used. These polishing units 25 </ b> A and 25 </ b> B are arranged symmetrically with respect to the center of the wafer W held by the wafer holding unit 3. Since the polishing units 25A and 25B have the same configuration as that of the polishing unit 25 shown in FIG.

  The first polishing unit 25A has a first polishing tape 38A with a rough edge on the wafer W, and the second polishing unit 25B performs a second polishing with a fine edge on the wafer W. It has a tape 38B. FIG. 7 is a diagram for explaining a method of polishing a wafer using the polishing apparatus shown in FIG.

  In Step 1, the first polishing tape 38A and the first polishing tape 38A are pressed so that a part of the first polishing tape 38A slightly protrudes from the pressing pad 51 of the first polishing unit 25A inward in the radial direction of the wafer W. The pad 51 is positioned. In step 2, the pressing pad 51 is pushed down by the vertical movement mechanism 59 of the first polishing unit 25A so that the polishing surface of the first polishing tape 38A is pressed against the edge portion of the rotating wafer W, and the vertical surface faces the edge portion of the wafer W. Then, a horizontal plane is formed (first polishing step). The inner edge portion of the pressing pad 51 during polishing is pressed against the edge portion of the wafer W via the first polishing tape 38A. In step 3, the pressing pad 51 of the first polishing unit 25 </ b> A and the first polishing tape 38 </ b> A are raised by the vertical moving mechanism 59, and the first polishing tape 38 </ b> A is separated from the wafer W.

  In Step 4, the second polishing tape 38B and the pressing pad 51 are so projected that a part of the second polishing tape 38B protrudes inward in the radial direction of the wafer W from the pressing pad 51 of the second polishing unit 25B. And are positioned. The inner edge of the second polishing tape 38B is located radially inward of the vertical surface of the wafer W, and the inner edge of the pressing pad 51 of the second polishing unit 25B is radial in the vertical surface of the wafer W. Located on the outside. The horizontal distance between the inner edge of the pressing pad 51 of the second polishing unit 25B and the vertical surface of the wafer W is larger than the thickness of the second polishing tape 38B.

  In step 5, the pressing pad 51 and the second polishing tape 38B are lowered by the vertical movement mechanism 59 of the second polishing unit 25B. In step 6, a part (protrusion) of the second polishing tape 38B is moved to the wafer W. A part of the second polishing tape 38B is bent upward by pressing against the corner where the vertical surface and the surface (upper surface) intersect. This corner is formed at the edge of the wafer W by the first polishing process. In step 7, the vertical surface is polished by the bent portion of the second polishing tape 38B by pressing the pressing pad 51 inward in the radial direction of the wafer W by the radial movement mechanism 45 of the second polishing unit 25B. (Second polishing step). When the second polishing tape 38B is bent, the polishing surface comes into contact with the vertical surface of the wafer edge portion. Therefore, the vertical surface of the wafer W is polished by the polishing surface of the second polishing tape 38B. At least one of the first polishing step and the second polishing step may be performed while moving the polishing tape in the longitudinal direction. In this case, in order to increase the polishing rate of the wafer W, it is preferable that the moving direction of the polishing tape opposes the traveling direction of the edge portion of the rotating wafer W. Furthermore, it is preferable to move the polishing tape 38 in the radial direction of the wafer W while pressing the polishing tape 38 against the edge portion of the wafer W in order to remove polishing marks.

  According to the present embodiment, a smoother vertical surface can be formed at the edge portion of the wafer W by the fine second polishing tape. Furthermore, multistage polishing can be performed with different types of polishing tapes while the wafer W is held by the wafer holder 3. In the present embodiment, it is not necessary to transfer the wafer W between the first polishing process and the second polishing process, and the centering shift of the wafer between the first polishing process and the second polishing process can be eliminated. There is an advantage that you can. It is also possible to arrange three or more polishing units.

  Next, still another embodiment of the polishing method according to the present invention will be described. FIGS. 8A to 8E are views for explaining still another embodiment of the polishing method according to the present invention. In this embodiment, the polishing tape polishes the edge portion of the wafer W a plurality of times while sliding on the edge portion of the wafer W in the radial direction of the wafer W. Specifically, as shown in FIG. 8A, the polishing tape 38 is pushed to the edge portion of the wafer W by the pressing pad 51 in a state where a part of the polishing tape 38 protrudes radially inward from the pressing pad 51. Further, the polishing tape 38 and the pressing pad 51 are moved inward in the radial direction of the wafer W while the polishing tape 38 is in contact with the edge portion. The polishing tape 38 slides on the edge portion until a predetermined stop position is reached, and polishes the edge portion.

  Similarly, as shown in FIGS. 8B to 8E, the slide polishing step of sliding the polishing tape 38 on the edge portion is repeated. Each time the slide polishing process is performed, the stop position of the polishing tape 38 is moved slightly inward in the radial direction of the wafer W. In this way, by repeating the slide polishing process while gradually moving the stop position of the polishing tape 38 to the inside, a reverse taper surface as shown in FIG. After the polishing tape 38 reaches a predetermined stop position, before starting the next slide polishing process, the pressing pad 51 and the polishing tape 38 are once separated from the wafer W and moved to the start position of the next slide polishing process. Alternatively, the pressing pad 51 and the polishing tape 38 may be slid radially outward of the wafer W and moved to the start position of the next slide polishing step. Also in this embodiment, the slide polishing step may be performed while moving the polishing tape 38 in the longitudinal direction. In this case, in order to increase the polishing rate of the wafer W, it is preferable that the moving direction of the polishing tape 38 opposes the traveling direction of the edge portion of the rotating wafer W.

  The reverse tapered surface formed on the edge portion by the slide polishing shown in FIGS. 8B to 8E is advantageous for manufacturing an SOI (Silicon on Insulator) substrate. The SOI substrate is manufactured by bonding a device wafer and a silicon wafer. More specifically, as shown in FIGS. 9A and 9B, the device wafer W1 and the silicon wafer W2 are bonded together, and the bonded device wafer W1 and the silicon wafer W2 are inverted, and FIG. As shown in FIG. 9C, the SOI wafer as shown in FIG. 9D is obtained by grinding the device wafer W1 from the back surface with a grinder. As can be seen from FIG. 9D, the end surface of the device layer on the silicon wafer W2 is an inversely tapered surface, so that there is an advantage that the device layer is hardly damaged.

  FIG. 10 is a view for explaining still another embodiment of the polishing method according to the present invention. Since the configuration and operation of the present embodiment that are not particularly described are the same as those of the above-described embodiment, a duplicate description thereof is omitted. The present embodiment is the same as the above-described embodiment in that the polishing tape 38 is arranged along the tangential direction of the wafer W. However, in this embodiment, the edge of the pressing pad 51 matches the edge of the polishing tape 38. In this state, the polishing pad 38 is pressed against the edge portion of the wafer W by the pressing pad 51 to polish the edge portion of the wafer W, which is different from the above-described embodiment.

  The polishing method according to this embodiment includes a first polishing process that is an initial stage polishing process, a second polishing process that is a high removal rate polishing process, and a third polishing process that is a final stage polishing process. The first polishing step is a step of pressing the edge of the polishing tape 38 against the edge of the wafer W with the first pressing pressure by the pressing pad 51 while rotating the wafer W. The second polishing step is a step of pressing the edge of the polishing tape 38 against the edge portion of the wafer W with the second pressing pressure higher than the first pressing pressure by the pressing pad 51 while rotating the wafer W. . The third polishing step is a step of pressing the edge portion of the polishing tape 38 against the edge portion of the wafer W with the third pressing pressure lower than the second pressing pressure by the pressing pad 51 while rotating the wafer W. It is. In the first polishing step, the second polishing step, and the third polishing step, the edge portion of the polishing tape 38 is pressed against the edge portion of the wafer W by the edge portion of the pressing pad 51, and thereby the surface perpendicular to the edge portion of the wafer W is obtained. And a horizontal plane is formed.

  In the first polishing step, the second polishing step, and the third polishing step, the pressing pressure of the polishing tape 38 against the wafer W and the rotation speed of the wafer W can be appropriately changed. For example, it is preferable that the wafer W is rotated at a first rotation speed in the first polishing step, and is rotated at a second rotation speed higher than the first rotation speed in the second polishing step. The rotation speed of the wafer W in the third polishing step may be the same as the first rotation speed or the same as the second rotation speed. Further, the third pressing pressure in the third polishing step may be the same as the first pressing pressure in the first polishing step, or may be lower than the first pressing pressure, or the first pressing pressure. May be higher.

  In the first polishing step, since the wafer W is polished slowly with a low pressing pressure, a corner portion perpendicular to the edge portion of the wafer W can be formed without causing a defect in the corner portion. In the second polishing step, since the wafer W is polished with a high pressing pressure, the entire polishing time can be shortened. In the third polishing step, since the wafer W is polished with a low pressing pressure, the surface roughness can be improved. An additional polishing step may be performed after the third polishing step.

  In the present embodiment, the flat portion including the edge of the polishing tape 38 is pressed against the edge portion of the wafer W in a state where the edge of the polishing tape 38 and the edge of the pressing pad 51 are aligned. The edge of the polishing tape 38 is a right-angled corner, and this right-angled edge is pressed from above onto the peripheral edge of the wafer W by the edge of the pressing pad 51. Therefore, as shown in FIG. 10, the cross-sectional shape of the polished wafer W can be made to be a right angle. The first polishing step, the second polishing step, and the third polishing step may be performed while moving the polishing tape 38 in the longitudinal direction. In this case, in order to increase the polishing rate of the wafer W, it is preferable that the moving direction of the polishing tape 38 opposes the traveling direction of the edge portion of the rotating wafer W.

  Next, details of a polishing apparatus capable of executing the above-described embodiment of the polishing method will be described. 11 is a plan view showing the polishing apparatus, FIG. 12 is a cross-sectional view taken along line FF in FIG. 11, and FIG. 13 is a view seen from the direction indicated by arrow G in FIG. The polishing apparatus includes a wafer holding unit 3 that horizontally holds and rotates a wafer (substrate) W that is an object to be polished. FIG. 11 shows a state in which the wafer holding unit 3 holds the wafer W. The wafer holding unit 3 includes a holding stage 4 that holds the lower surface of the wafer W by vacuum suction, a hollow shaft 5 that is connected to the center of the holding stage 4, and a motor M 1 that rotates the hollow shaft 5. . The wafer W is placed on the holding stage 4 so that the center of the wafer W coincides with the axis of the hollow shaft 5.

  The holding stage 4 is disposed in a polishing chamber 22 formed by a partition wall 20 and a base plate 21. The partition wall 20 includes a transfer port 20 a for carrying the wafer W into and out of the polishing chamber 22. The conveyance port 20a is formed as a notch extending horizontally. The transport port 20 a can be closed by a shutter 23.

  The hollow shaft 5 is supported by a ball spline bearing (linear motion bearing) 6 so as to be movable up and down. A groove 4 a is formed on the upper surface of the holding stage 4, and this groove 4 a communicates with a communication path 7 extending through the hollow shaft 5. The communication path 7 is connected to a vacuum line 9 via a rotary joint 8 attached to the lower end of the hollow shaft 5. The communication path 7 is also connected to a nitrogen gas supply line 10 for detaching the processed wafer W from the holding stage 4. By switching between the vacuum line 9 and the nitrogen gas supply line 10, the wafer W is held on the upper surface of the holding stage 4 and separated.

  The hollow shaft 5 is rotated by the motor M1 via a pulley p1 connected to the hollow shaft 5, a pulley p2 attached to a rotation shaft of the motor M1, and a belt b1 hung on the pulleys p1 and p2. . The ball spline bearing 6 is a bearing that allows the hollow shaft 5 to freely move in the longitudinal direction thereof. The ball spline bearing 6 is fixed to a cylindrical casing 12. Therefore, the hollow shaft 5 can move linearly up and down with respect to the casing 12, and the hollow shaft 5 and the casing 12 rotate integrally. The hollow shaft 5 is connected to an air cylinder (elevating mechanism) 15, and the hollow shaft 5 and the holding stage 4 can be raised and lowered by the air cylinder 15.

  A radial bearing 18 is interposed between the casing 12 and a cylindrical casing 14 disposed concentrically on the outside thereof, and the casing 12 is rotatably supported by the bearing 18. With such a configuration, the wafer holding unit 3 can rotate the wafer W around its central axis and raise and lower the wafer W along its central axis.

  A polishing unit 25 for polishing the peripheral edge of the wafer W is disposed outside the wafer W held in the wafer holding unit 3 in the radial direction. The polishing unit 25 is disposed inside the polishing chamber 22. As shown in FIG. 13, the entire polishing unit 25 is fixed on the installation table 27. The installation table 27 is connected to the polishing unit moving mechanism 30 via the arm block 28.

  The polishing unit moving mechanism 30 includes a ball screw mechanism 31 that holds the arm block 28, a motor 32 that drives the ball screw mechanism 31, and a power transmission mechanism 33 that connects the ball screw mechanism 31 and the motor 32. Yes. The power transmission mechanism 33 includes a pulley and a belt. When the motor 32 is operated, the ball screw mechanism 31 moves the arm block 28 in the direction indicated by the arrow in FIG. 13 and the entire polishing unit 25 moves in the tangential direction of the wafer W. The polishing unit moving mechanism 30 also functions as an oscillation mechanism that swings the polishing unit 25 at a predetermined amplitude and a predetermined speed.

  The polishing unit 25 includes a polishing head 50 that polishes the peripheral portion of the wafer W using the polishing tape 38, and a polishing tape supply and recovery mechanism 70 that supplies the polishing tape 38 to the polishing head 50 and collects it from the polishing head 50. ing. The polishing head 50 is a top edge polishing head that presses the polishing surface of the polishing tape 38 against the peripheral edge of the wafer W from above to polish the top edge portion of the wafer W. The polishing tape supply / recovery mechanism 70 also functions as a polishing tape support mechanism that supports the polishing tape 38 in parallel with the surface of the wafer W.

  14 is a plan view of the polishing head 50 and the polishing tape supply / recovery mechanism 70, FIG. 15 is a front view of the polishing head 50 and the polishing tape supply / recovery mechanism 70, and FIG. 16 is a cross-sectional view taken along line HH shown in FIG. 17 is a side view of the polishing tape supply / recovery mechanism 70 shown in FIG. 15, and FIG. 18 is a longitudinal sectional view of the polishing head 50 shown in FIG.

  Two linear motion guides 40A and 40B extending in parallel with the radial direction of the wafer W are arranged on the installation table 27. The polishing head 50 and the linear motion guide 40A are connected via a connection block 41A. Further, the polishing head 50 is connected to a motor 42A and a ball screw 43A that move the polishing head 50 along the linear motion guide 40A (that is, in the radial direction of the wafer W). More specifically, the ball screw 43A is fixed to the connection block 41A, and the motor 42A is fixed to the installation base 27 via the support member 44A. The motor 42A is configured to rotate the screw shaft of the ball screw 43A, whereby the connecting block 41A and the polishing head 50 connected thereto are moved along the linear guide 40A. The motor 42A, the ball screw 43A, and the linear guide 40A constitute a first moving mechanism 45 that moves the polishing head 50 in the radial direction of the wafer W held by the wafer holding unit 3.

  Similarly, the polishing tape supply / recovery mechanism 70 and the linear motion guide 40B are coupled via a coupling block 41B. Further, the polishing tape supply / recovery mechanism 70 is connected to a motor 42B and a ball screw 43B that move the polishing tape supply / recovery mechanism 70 along the linear motion guide 40B (that is, in the radial direction of the wafer W). More specifically, the ball screw 43B is fixed to the connection block 41B, and the motor 42B is fixed to the installation base 27 via the support member 44B. The motor 42B is configured to rotate the screw shaft of the ball screw 43B, whereby the connecting block 41B and the polishing tape supply / recovery mechanism 70 connected thereto are moved along the linear motion guide 40B. The motor 42B, the ball screw 43B, and the linear motion guide 40B are a tape moving mechanism that moves the polishing tape 38 and the polishing tape supply / recovery mechanism (polishing tape support mechanism) 70 in the radial direction of the wafer W held by the wafer holding unit 3. (Second moving mechanism) 46 is configured.

  As shown in FIG. 18, the polishing head 50 presses down the pressing pad 51 that presses the polishing tape 38 against the wafer W, the pad holder 52 that holds the pressing pad 51, and the pad holder 52 (and the pressing pad 51). And an air cylinder 53 as a pressing mechanism. The air cylinder 53 is held by a holding member 55. Further, the holding member 55 is connected to an air cylinder 56 as a lift mechanism via a linear motion guide 54 extending in the vertical direction. When a gas such as air is supplied to the air cylinder 56 from a gas supply source (not shown), the air cylinder 56 pushes up the holding member 55. Thereby, the holding member 55, the air cylinder 53, the pad holder 52, and the pressing pad 51 are lifted along the linear motion guide 54.

  In the present embodiment, the vertical movement mechanism 59 that moves the pressing pad 51 in a direction perpendicular to the wafer surface is constituted by an air cylinder 53 and an air cylinder 56. Further, the first moving mechanism 45 including the motor 42A, the ball screw 43A, and the linear guide 40A also functions as a radial moving mechanism that moves the pressing pad 51 and the vertical moving mechanism 59 in the radial direction of the wafer W. To do.

  The air cylinder 56 is fixed to an installation member 57 fixed to the connection block 41A. The installation member 57 and the pad holder 52 are connected via a linear guide 58 extending in the vertical direction. When the pad holder 52 is pushed down by the air cylinder 53, the pressing pad 51 moves downward along the linear motion guide 58 and presses the polishing tape 38 against the edge portion of the wafer W. The pressing pad 51 is made of a resin such as PEEK (polyether ether ketone), a metal such as stainless steel, or a ceramic such as SiC (silicon carbide).

  The pressing pad 51 has a plurality of through holes 51a extending in the vertical direction, and a vacuum line 60 is connected to the through holes 51a. The vacuum line 60 is provided with a valve (not shown) so that a vacuum is formed in the through hole 51a of the pressing pad 51 by opening the valve. When a vacuum is formed in the through hole 51 a with the pressing pad 51 in contact with the upper surface of the polishing tape 38, the upper surface of the polishing tape 38 is held on the lower surface of the pressing pad 51. Note that the number of the through holes 51a of the pressing pad 51 may be one. The shape of the through hole 51a is not particularly limited as long as the polishing tape 38 is securely held by the pressing pad 51 by vacuum. For example, the through hole 51a may have a slit shape, or one or a plurality of through holes 51a having different shapes may be provided.

  The pad holder 52, the air cylinder 53, the holding member 55, the air cylinder 56, and the installation member 57 are accommodated in the box 62. The lower part of the pad holder 52 protrudes from the bottom of the box 62, and the pressing pad 51 is attached to the lower part of the pad holder 52. A position sensor 63 for detecting the vertical position of the pressing pad 51 is disposed in the box 62. The position sensor 63 is attached to the installation member 57. The pad holder 52 is provided with a dog 64 as a sensor target, and the position sensor 63 detects the vertical position of the pressing pad 51 from the vertical position of the dog 64.

  FIG. 19 is a view of the position sensor 63 and the dog 64 as seen from above. The position sensor 63 includes a light projecting unit 63A and a light receiving unit 63B. When the dog 64 is lowered together with the pad holder 52 (and the pressing pad 51), a part of the light emitted from the light projecting unit 63A is blocked by the dog 64. Therefore, the position of the dog 64, that is, the position of the pressing pad 51 in the vertical direction can be detected from the amount of light received by the light receiving unit 63B. The position sensor 63 shown in FIG. 19 is a so-called transmission type optical sensor, but other types of position sensors may be used.

  The polishing tape supply / recovery mechanism 70 includes a supply reel 71 for supplying the polishing tape 38 to the polishing head 50 and a recovery reel 72 for recovering the polishing tape 38 from the polishing head 50. The supply reel 71 and the recovery reel 72 are connected to tension motors 73 and 74, respectively. The tension motors 73 and 74 can apply a predetermined tension to the polishing tape 38 by applying a predetermined torque to the supply reel 71 and the recovery reel 72.

  A polishing tape feed mechanism 76 is provided between the supply reel 71 and the recovery reel 72. The polishing tape feeding mechanism 76 includes a tape feeding roller 77 that feeds the polishing tape 38, a nip roller 78 that presses the polishing tape 38 against the tape feeding roller 77, and a tape feeding motor 79 that rotates the tape feeding roller 77. Yes. The polishing tape 38 is sandwiched between the nip roller 78 and the tape feed roller 77. By rotating the tape feed roller 77 in the direction indicated by the arrow in FIG. 15, the polishing tape 38 is fed from the supply reel 71 to the collection reel 72.

  The tension motors 73 and 74 and the tape feed motor 79 are installed on the base 81. The base 81 is fixed to the connection block 41B. The base 81 has two support arms 82 and 83 extending from the supply reel 71 and the recovery reel 72 toward the polishing head 50. A plurality of guide rollers 84A, 84B, 84C, 84D, and 84E that support the polishing tape 38 are attached to the support arms 82 and 83. The polishing tape 38 is guided by these guide rollers 84A to 84E so as to surround the polishing head 50.

  The extending direction of the polishing tape 38 is perpendicular to the radial direction of the wafer W when viewed from above. Two guide rollers 84D and 84E located below the polishing head 50 support the polishing tape 38 so that the polishing surface of the polishing tape 38 is parallel to the surface (upper surface) of the wafer W. Further, the polishing tape 38 between the two guide rollers 84D and 84E extends in parallel to the tangential direction of the wafer W. A gap is formed between the polishing tape 38 and the wafer W in the vertical direction.

  The polishing apparatus further includes a tape edge detection sensor 100 that detects the position of the edge of the polishing tape 38. The tape edge detection sensor 100 is a transmissive optical sensor, similar to the position sensor 63 described above. The tape edge detection sensor 100 includes a light projecting unit 100A and a light receiving unit 100B. As shown in FIG. 14, the light projecting unit 100A is fixed to the installation table 27, and the light receiving unit 100B is fixed to the base plate 21 forming the polishing chamber 22, as shown in FIG. The tape edge detection sensor 100 is configured to detect the position of the edge of the polishing tape 38 from the amount of light received by the light receiving unit 100B.

  When polishing the wafer W, as shown in FIG. 20, the polishing head 50 and the polishing tape supply / recovery mechanism 70 are moved to predetermined polishing positions by the motors 42A and 42B and the ball screws 43A and 43B, respectively. The polishing tape 38 in the polishing position extends in the tangential direction of the wafer W when viewed from above the wafer W. Therefore, the polishing tape supply / recovery mechanism 70 functions as a polishing tape support mechanism that supports the polishing tape 38 parallel to the surface of the wafer W in a state along the tangential direction of the wafer W.

  21 shows the pressing pad 51, the polishing tape 38, and the wafer W at the polishing position when the polishing method shown in FIGS. 3A to 3D and the polishing method shown in FIGS. It is the schematic diagram seen from the horizontal direction. As shown in FIG. 21, the polishing tape 38 is positioned above the edge portion of the wafer W, and the pressing pad 51 is positioned above the polishing tape 38. FIG. 22 is a view showing a state in which the polishing tape 38 is pressed against the wafer W by the pressing pad 51.

  FIG. 23 is a schematic view of the pressing pad 51, the polishing tape 38, and the wafer W viewed from the lateral direction when the polishing method shown in FIG. 10 is performed. As shown in FIG. 23, the edge of the pressing pad 51 at the polishing position and the edge of the polishing tape 38 coincide. That is, the polishing head 50 and the polishing tape supply / recovery mechanism 70 are independently moved to the polishing position so that the edge of the pressing pad 51 and the edge of the polishing tape 38 coincide. However, the edge of the pressing pad 51 and the edge of the polishing tape 38 do not have to be completely coincident, and the edge of the polishing tape 38 may protrude from the edge of the pressing pad 51 by about 20 μm to 100 μm.

  The polishing tape 38 is an elongated strip-shaped polishing tool. The width of the polishing tape 38 is basically constant over its entire length, but there may be some variation in the width depending on the portion of the polishing tape 38. For this reason, there exists a possibility that the position of the edge part of the polishing tape 38 in a grinding | polishing position may differ for every wafer. On the other hand, the position of the pressing pad 51 in the polishing position is always constant. Therefore, in order to align the edge of the polishing tape 38 with the edge of the pressing pad 51, the position of the edge of the polishing tape 38 is detected by the above-described tape edge detection sensor 100 before being moved to the polishing position.

  FIG. 24A to FIG. 24C are diagrams for explaining the operation when the edge of the polishing tape 38 is detected. Prior to the polishing of the wafer W, the polishing tape 38 is moved from the retracted position shown in FIG. 24A to the tape edge detection position shown in FIG. At the tape edge detection position, the tape edge detection sensor 100 detects the position of the edge of the polishing tape 38 on the wafer side. Then, as shown in FIG. 24C, a part of the polishing tape 38 protrudes from the edge of the pressing pad 51 by a predetermined width, or as shown in FIG. The polishing tape 38 is moved to the polishing position so as to coincide with the edge of the tape.

  The position of the edge of the pressing pad 51 at the polishing position is stored in advance in the polishing control unit 11 (see FIG. 11). Therefore, the polishing control unit 11 can calculate the movement distance of the polishing tape 38 from the detected position of the edge of the polishing tape 38 and the position of the edge of the pressing pad 51. In this way, since the moving distance of the polishing tape 38 is determined based on the detected position of the edge of the polishing tape 38, the polishing tape 38 is moved to a predetermined position regardless of variations in the width of the polishing tape 38. Can be made.

  Next, the polishing operation of the polishing apparatus configured as described above will be described. The operation of the polishing apparatus described below is controlled by the polishing control unit 11 shown in FIG. The wafer W is held by the wafer holding unit 3 so that a film (for example, a device layer) formed on the surface thereof faces upward, and is further rotated around the center of the wafer W. A liquid (for example, pure water) is supplied to the center of the rotating wafer W from a liquid supply mechanism (not shown). The pressing pad 51 and the polishing tape 38 of the polishing head 50 are each moved to a predetermined polishing position as shown in FIG.

  FIG. 25A shows the polishing tape 38 and the pressing pad 51 in the polishing position as viewed from the radial direction of the wafer W. The pressing pad 51 shown in FIG. 25A is lifted by the air cylinder 56 (see FIG. 18), and the pressing pad 51 is located above the polishing tape 38. Next, the operation of the air cylinder 56 is stopped and its piston rod is lowered, and the pressing pad 51 is lowered until its lower surface comes into contact with the upper surface of the polishing tape 38 as shown in FIG. In this state, a vacuum is formed in the through hole 51 a of the pressing pad 51 through the vacuum line 60, and the polishing tape 38 is held on the lower surface of the pressing pad 51. While holding the polishing tape 38, the pressing pad 51 is lowered by the air cylinder 53 (see FIG. 18). As shown in FIG. 25C, the pressing pad 51 uses the polishing surface of the polishing tape 38 as the peripheral edge of the wafer W. Press against the part with a predetermined polishing pressure. The polishing pressure is a pressing pressure that acts on the peripheral edge of the wafer W from the polishing tape 38. This polishing pressure can be adjusted by the pressure of the gas supplied to the air cylinder 53.

  The edge portion of the wafer W is polished by sliding contact between the rotating wafer W and the polishing tape 38. In order to increase the polishing rate of the wafer W, the polishing tape 38 and the pressing pad 51 may be swung along the tangential direction of the wafer W by the polishing unit moving mechanism 30 during polishing of the wafer W. During polishing, a liquid (for example, pure water) is supplied to the central portion of the rotating wafer W, and the wafer W is polished in the presence of water. The liquid supplied to the wafer W spreads over the entire upper surface of the wafer W due to centrifugal force, thereby preventing polishing dust from adhering to the device formed on the wafer W. As described above, during polishing, the polishing tape 38 is held on the pressing pad 51 by vacuum suction, so that the positions of the polishing tape 38 and the pressing pad 51 are prevented from shifting. Therefore, the polishing position and the polishing shape can be stabilized. Furthermore, even if the polishing pressure is increased, the polishing tape 38 and the pressing pad 51 are not displaced from each other, so that the polishing time can be shortened.

  The position of the pressing pad 51 during polishing of the wafer W in the vertical direction is detected by the position sensor 63. Therefore, the polishing end point can be detected from the vertical position of the pressing pad 51. For example, the polishing of the edge portion of the wafer W can be completed when the vertical position of the pressing pad 51 reaches a predetermined target position. This predetermined target position is determined according to the target polishing amount.

  When the polishing of the wafer W is completed, the supply of gas to the air cylinder 53 is stopped, whereby the pressing pad 51 is raised to the position shown in FIG. At the same time, the vacuum suction of the polishing tape 38 is stopped. Further, the pressing pad 51 is raised to the position shown in FIG. Then, the polishing head 50 and the polishing tape supply / recovery mechanism 70 are moved to the retracted position shown in FIG. The polished wafer W is raised by the wafer holding unit 3 and carried out of the polishing chamber 22 by a hand of a transfer mechanism (not shown). Before the polishing of the next wafer starts, the polishing tape 38 is fed from the supply reel 71 to the recovery reel 72 by a predetermined distance by the tape feeding mechanism 76. Thus, the new polishing surface is used for polishing the next wafer. When it is estimated that the polishing tape 38 is clogged with polishing scraps, the polished wafer W may be polished again with a new polishing surface after the polishing tape 38 has been fed a predetermined distance. The clogging of the polishing tape 38 can be estimated from, for example, the polishing time and the polishing pressure.

  The wafer W may be polished while the polishing tape 38 is fed (moved) at a predetermined speed by the tape feeding mechanism 76 in the longitudinal direction. In this case, in order to increase the polishing rate of the wafer W, it is preferable that the moving direction of the polishing tape 38 opposes the traveling direction of the edge portion of the rotating wafer W. It is also possible to feed the polishing tape 38 in the longitudinal direction by the tape feeding mechanism 76 while holding the polishing tape 38 on the pressing pad 51 by vacuum suction. In some cases, the polishing tape 38 may not be held on the pressing pad 51 by vacuum suction.

  As shown in FIG. 26A, when the polishing pressure on the wafer W is increased, the wafer W is greatly bent by the polishing pressure of the pressing pad 51. As a result, as shown in FIG. The surface to be polished may be inclined. Therefore, in the embodiment shown in FIG. 27, a support stage 180 that supports the peripheral edge of the wafer W from below is provided in the wafer holding unit 3. Other configurations that are not particularly described are the same as those shown in FIG. The support stage 180 is fixed to the support stage base 181. The support stage base 181 is fixed to the upper end of the casing 12 and rotates integrally with the casing 12. Therefore, the support stage 180 rotates integrally with the casing 12 and the holding stage 4.

  The support stage 180 has an inverted truncated cone shape as shown in FIG. 28 in order to support the entire lower surface of the peripheral edge of the wafer W. The lower surface of the peripheral portion of the wafer W supported by the support stage 180 is a region including at least the bottom edge portion E2 shown in FIGS. 36 (a) and 36 (b). An annular upper surface 180 a of the support stage 180 constitutes a support surface that supports the lower surface of the peripheral edge of the wafer W. At the time of polishing the wafer W, the outermost peripheral end of the support stage 180 and the outermost peripheral end of the wafer W substantially coincide with each other.

  By using such a support stage 180, even if the pressing pad 51 presses the polishing tape 38 against the wafer W, the wafer W does not bend. Therefore, by polishing the edge portion of the wafer W with the polishing tape 38, a vertical surface and a horizontal surface can be formed on the edge portion of the wafer W. Further, since the support stage 180 supports the entire lower surface of the peripheral edge of the wafer W, the edge portion of the wafer W can be uniformly polished as compared with a conventional wafer support mechanism that supports only a part of the wafer. .

  Since the ball spline bearing 6 is disposed between the hollow shaft 5 and the casing 12, the hollow shaft 5 can move in the vertical direction with respect to the casing 12. Therefore, the holding stage 4 connected to the upper end of the hollow shaft 5 can move in the vertical direction relative to the casing 12 and the support stage 180. FIG. 29 shows a state in which the holding stage 4 and the wafer W held on the upper surface thereof are raised relative to the support stage 180.

  The polishing tape 38 may receive a load in the horizontal direction due to the effect of contact with the wafer W and the shape of the peripheral edge of the wafer W. As a result, the polishing tape 38 may escape to the outside of the wafer W. Therefore, as shown in FIG. 30, a tape stopper 185 that restricts the horizontal movement of the polishing tape 38 is provided on the pressing pad 51. The tape stopper 185 is disposed outside the polishing tape 38 in the radial direction of the wafer W, and restricts the movement of the polishing tape 38 to the outside. The tape stopper 185 arranged in this way can prevent the polishing tape 38 from escaping to the outside of the wafer W. Therefore, the polishing shape and polishing width of the wafer W can be stabilized.

  When the outward movement of the polishing tape 38 is received by the tape stopper 185, the polishing tape 38 may be distorted as shown in FIG. Therefore, in the embodiment shown in FIG. 32, a tape cover 186 is provided close to the polishing surface of the polishing tape 38 in order to prevent the polishing tape 38 from being distorted. The tape cover 186 is fixed to the tape stopper 185 and is disposed so as to cover most of the polishing surface of the polishing tape 38. The tape cover 186 is disposed below the polishing tape 38, and a minute gap dg is formed between the polishing surface of the polishing tape 38 and the upper surface of the tape cover 186. The polishing tape 38 is disposed between the pressing pad 51 and the tape cover 186. By providing such a tape cover 186, the polishing tape 38 is prevented from being distorted, and the polishing tape 38 can be kept flat. Therefore, the polishing shape and polishing width of the wafer W can be stabilized.

  As shown in FIG. 32, the polishing tape 38 is disposed in a space surrounded by the pressing pad 51, the tape stopper 185, and the tape cover 186. A gap h between the lower surface of the pressing pad 51 and the upper surface of the tape cover 186 is set to be larger than the thickness of the polishing tape 38. A gap dg between the polishing tape 38 and the tape cover 186 is smaller than the thickness of the wafer W.

  The inner side surface 186 a of the tape cover 186 is located outside the edge portion 51 b of the pressing pad 51 in the radial direction of the wafer W. Therefore, the polishing surface of the polishing tape 38 is exposed by the distance dw between the edge of the polishing tape 38 and the inner surface 186a of the tape cover 186. The polishing of the wafer W is performed on the exposed polished surface.

  In the structure shown in FIG. 32, since the tape stopper 185 receives the horizontal load acting on the polishing tape 38, the pressing pad 51 may move outward together with the polishing tape 38. Such movement of the pressing pad 51 makes the polishing shape and the polishing width unstable. In view of this, in the embodiment shown in FIG. 33, a movement restriction mechanism for restricting the outward movement of the pressing pad 51 is provided. The movement restriction mechanism includes a protrusion member 190 fixed to the pressing pad 51 and a side stopper 191 that restricts the movement of the protrusion member 190 in the horizontal direction. In the present embodiment, a plunger is used as the protruding member 190.

  The side stopper 191 is disposed outside the plunger (protruding member) 190 in the radial direction of the wafer W, and receives the movement of the plunger 190 to the outside. The side stopper 191 is fixed to the lower surface of the box 62 of the polishing head 50, and the position of the side stopper 191 is fixed. The plunger 190 and the side stopper 191 are disposed close to each other, and the gap dr between the plunger 190 and the side stopper 191 is 10 μm to 100 μm. According to such a configuration, when the pressing pad 51 receives a horizontal load from the polishing tape 38 and moves to the outside during polishing, the plunger 190 comes into contact with the side stopper 191, thereby the outside of the pressing pad 51 and the polishing tape 38. Movement to is restricted. Therefore, the polishing shape and polishing width of the wafer W can be stabilized.

  The embodiments shown in FIGS. 27 to 33 can be combined as appropriate. For example, FIG. 34 shows an example in which the support stage 180 shown in FIG. 27 and the polishing head 50 shown in FIG. 33 are combined. According to the configuration shown in FIG. 34, the wafer W is prevented from being bent, and the movement and distortion of the polishing tape 38 are prevented.

  FIG. 35 is a plan view showing a polishing apparatus including a plurality of polishing units. In this polishing apparatus, a first polishing unit 25A and a second polishing unit 25B are provided in the polishing chamber 22. Since the polishing units 25A and 25B have the same configuration as the above-described polishing unit 25, redundant description thereof will be omitted. The arrangement of these two polishing units 25 </ b> A and 25 </ b> B is symmetric with respect to the wafer W held by the wafer holding unit 3. The first polishing unit 25A can be moved by a first polishing unit moving mechanism (not shown), and the second polishing unit 25B can be moved by a second polishing unit moving mechanism (not shown). It has become. These first and second polishing unit moving mechanisms have the same configuration as the polishing unit moving mechanism 30 described above.

  Different types of polishing tape can be used in the first polishing unit 25A and the second polishing unit 25B. For example, the first polishing unit 25A can perform rough polishing of the wafer W, and the second polishing unit 25B can perform final polishing of the wafer W. The polishing method shown in FIG. 7 can be performed by using the polishing apparatus shown in FIG.

  The embodiment described above is described for the purpose of enabling the person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in the widest scope according to the technical idea defined by the claims.

DESCRIPTION OF SYMBOLS 3 Wafer holding part 4 Holding stage 11 Polishing control part 25 Polishing unit 27 Installation stand 30 Polishing unit moving mechanism 38 Polishing tape 40A, 40B Linear motion guide 45 Radial direction moving mechanism (1st moving mechanism)
46 Tape moving mechanism (second moving mechanism)
50 Polishing head 51 Press pad 52 Pad holder 53 Air cylinder 54 Linear motion guide 56 Air cylinder 59 Vertical movement mechanism 60 Vacuum line 63 Position sensor 64 Dog 70 Polishing tape supply and recovery mechanism (polishing tape support mechanism)
71 Supply reel 72 Collection reel 73, 74 Tension motor 76 Tape feed mechanism 82, 83 Support arm 84A, 84B, 84C, 84D, 84E Guide roller 100 Tape edge detection sensor 180 Support stage 181 Support stage base 185 Tape stopper 186 Tape cover 190 Plunger 191 Side stopper W Wafer

Claims (16)

Rotate the board
With a part of the polishing tape protruding from the pressing pad toward the inside in the radial direction of the substrate, the edge of the substrate is polished by pressing the polishing tape against the edge of the substrate with the pressing pad. While performing a first polishing step of bending the part of the polishing tape along the pressing pad,
Performing a second polishing step of further polishing the edge portion of the substrate with the polishing tape by pressing the part of the bent polishing tape toward the radially inner side of the substrate with the pressing pad. A characteristic polishing method.   2. The polishing method according to claim 1, wherein the part of the bent polishing tape is longer than a depth of a portion to be polished formed on an edge portion of the substrate by the first polishing step.   3. The polishing method according to claim 1, wherein at least one of the first polishing step and the second polishing step is performed while moving the polishing tape in a longitudinal direction thereof.   The polishing method according to claim 3, wherein the moving direction of the polishing tape opposes the traveling direction of the edge portion of the rotating substrate. The polishing tape in the first polishing step is a coarse polishing tape,
5. The polishing method according to claim 1, wherein the second polishing step is performed using a fine abrasive tape instead of the coarse abrasive tape. 6. Rotate the board
With a part of the polishing tape protruding from the pressing pad toward the inside in the radial direction of the substrate, the edge of the substrate is polished by pressing the polishing tape against the edge of the substrate with the pressing pad. Perform the first polishing step,
After the first polishing step, a part of the polishing tape is pressed against an edge portion of the substrate, and the part of the polishing tape is bent along the pressing pad,
Performing a second polishing step of further polishing the edge portion of the substrate with the polishing tape by pressing the part of the bent polishing tape toward the radially inner side of the substrate with the pressing pad. A characteristic polishing method.   The polishing method according to claim 6, wherein at least one of the first polishing step and the second polishing step is performed while moving the polishing tape in a longitudinal direction thereof.   The polishing method according to claim 7, wherein the moving direction of the polishing tape opposes the traveling direction of the edge portion of the rotating substrate. Rotate the board
In a state where a part of the first polishing tape protrudes radially inward of the substrate from the first pressing pad, the first polishing tape is moved to the edge portion of the substrate by the first pressing pad. Performing a first polishing step of pressing against the edge portion of the substrate,
Positioning the second polishing tape and the second pressing pad so that a part of the second polishing tape protrudes radially inward of the substrate from the second pressing pad,
The part of the second polishing tape is pressed against the corner part formed on the edge part of the substrate by the first polishing step by the second pressing pad. Is folded along the second pressing pad,
By pressing the part of the bent second polishing tape toward the inside in the radial direction of the substrate by the second pressing pad, the edge portion of the substrate is further polished by the second polishing tape. A polishing method comprising performing a second polishing step.   An end portion of the second pressing pad is located radially outside a vertical surface formed on the edge portion by the first polishing step, and the end portion of the second pressing pad and the vertical surface The positioning of the second polishing tape and the second pressing pad is performed such that the horizontal distance of the second polishing tape is larger than the thickness of the second polishing tape. Polishing method. The first abrasive tape is a coarse abrasive tape;
The polishing method according to claim 9 or 10, wherein the second polishing tape is a fine polishing tape.   The polishing method according to claim 9, wherein the first polishing step is performed while moving the first polishing tape in a longitudinal direction thereof.   The polishing method according to claim 12, wherein the moving direction of the first polishing tape opposes the traveling direction of the edge portion of the rotating substrate.   14. The polishing method according to claim 9, wherein the second polishing step is performed while moving the second polishing tape in a longitudinal direction thereof.   The polishing method according to claim 14, wherein the moving direction of the second polishing tape opposes the traveling direction of the edge portion of the rotating substrate. Rotate the board
While pressing the polishing tape against the edge portion of the substrate with the pressure pad, performing a slide polishing step of moving the polishing tape and the pressure pad toward the inside in the radial direction of the substrate until reaching a predetermined stop position,
Repeat the slide polishing process,
Each time the slide polishing process is performed, the polishing method is characterized in that the stop position is moved slightly inward in the radial direction.

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