JP4402106B2 - Polishing device - Google Patents

Description

  The present invention relates to a polishing apparatus that polishes a polishing object such as a semiconductor wafer in a flat and mirror-like shape, and more particularly to a polishing apparatus that includes a mechanism for controlling the polishing amount of a peripheral portion of the polishing object.

  In recent years, as semiconductor devices are highly integrated, circuit wiring is becoming finer and the distance between wirings is becoming narrower. In particular, in the case of photolithography having a line width of 0.5 μm or less, the allowable depth of focus becomes shallow, so that the flatness of the imaging surface of the stepper is required. Therefore, it is necessary to flatten the surface of the semiconductor wafer, but polishing is performed by a polishing apparatus as one means of this flattening method.

  Conventionally, this type of polishing apparatus has a turntable and a top ring, the top ring applies a constant pressure to the turntable, and an object to be polished is interposed between the turntable and the top ring, so that an abrasive liquid is obtained. The surface of the polishing object is polished to a flat and mirror surface.

In the polishing apparatus described above, if the relative pressing force between the polishing object being polished and the polishing cloth is not uniform over the entire surface of the polishing object, insufficient polishing or overpolishing depending on the pressing force of each part. Will occur. Therefore, in the conventional polishing apparatus, as a means for avoiding the unevenness of the pressing force,
(i) attaching an elastic mat such as polyurethane having elasticity to the semiconductor wafer holding surface of the top ring;
(ii) making the holding part of the polishing object, that is, the top ring tiltable with respect to the surface of the polishing cloth;
(iii) By preventing the peripheral portion of the polishing portion of the polishing cloth from being pressed independently of the top ring and the polishing object, the polishing region of the polishing cloth and the step around it are prevented;
Etc. are done.

  FIG. 12 is a diagram showing a main part of an example of a conventional polishing apparatus. The polishing apparatus supplies a polishing liquid 42 to the turntable 41 that rotates with a polishing cloth 42 on the upper surface, a top ring 45 that holds a semiconductor wafer 43 that is a polishing target so that it can be rotated and pressed, and the polishing cloth 42. A polishing liquid supply nozzle 48 is provided. The top ring 45 is connected to a top ring shaft 49, and the top ring 45 includes an elastic mat 47 such as polyurethane on the lower surface thereof, and holds the semiconductor wafer 43 in contact with the elastic mat 47. Further, the top ring 45 is provided with a cylindrical guide ring 46A at the outer peripheral edge portion so that the semiconductor wafer 43 does not come off from the lower surface of the top ring 45 during polishing. Here, the guide ring 46A is fixed to the top ring 45, and the lower end surface thereof is formed so as to protrude from the holding surface of the top ring 45, and the semiconductor wafer 43 which is a polishing object is held in the holding surface. In addition, it is prevented from jumping out of the top ring by frictional force with the polishing pad 42 during polishing.

  The semiconductor wafer 43 is held below the elastic mat 47 on the lower surface of the top ring 45, the semiconductor wafer 43 is pressed against the polishing cloth 42 on the turn table 41 by the top ring 45, and the turn table 41 and the top ring 45 are rotated. Then, the polishing cloth 42 and the semiconductor wafer 43 are moved relative to each other for polishing. At this time, the abrasive liquid Q is supplied from the abrasive liquid supply nozzle 48 onto the polishing cloth 42. As the abrasive liquid, for example, an abrasive solution in which abrasive grains made of fine particles are suspended is used, and a semiconductor wafer is polished by a combined action of a chemical polishing action by alkali and a mechanical polishing action by abrasive grains.

FIG. 13 is an enlarged cross-sectional view showing the state of the semiconductor wafer, polishing cloth, and elastic mat during polishing by the polishing apparatus shown in FIG. As shown in FIG. 13, when only the polishing object presses the polishing cloth, the periphery of the semiconductor wafer 43, which is the polishing object, is at the contact / non-contact boundary with the polishing cloth 42. At the same time, it is a boundary between contact / non-contact with the elastic mat 47. For this reason, the polishing pressure applied to the polishing object is non-uniform at the periphery of the polishing object that is the boundary between them, and only the periphery of the polishing object is polished much, which causes a so-called “dragging”. was there.
In order to prevent the edge of the semiconductor wafer described above, the present applicant previously proposed a polishing apparatus having a structure for pressing a polishing cloth located on the outer peripheral side of a semiconductor wafer in Japanese Patent Application No. 9-105252. ing.

  FIG. 14 is a diagram showing a polishing apparatus proposed in Japanese Patent Application No. 9-105252. In FIG. 14, reference numeral 51 denotes a top ring. The top ring 51 includes a top ring main body 51 </ b> A and a retainer ring 51 </ b> B detachably fixed to the outer peripheral portion of the top ring main body 51 </ b> A by a bolt 181. The recess 51a for housing the upper ring is formed by the lower surface of the top ring body 51A and the retainer ring 51B. The upper surface of the semiconductor wafer 54 is held by the lower surface of the top ring body 51A, and the outer peripheral portion of the semiconductor wafer 54 is held by the retainer ring 51B. A pressing ring 53 is provided around the top ring main body 51A and the retainer ring 51B so as to be movable up and down. Further, between the pressing ring 53 and the top ring 51, there is a substantially U-shaped cross section for preventing the top ring 51 and the pressing ring from coming into direct contact and suppressing excessive tilting of the top ring 51. A leaf spring 67 is interposed.

  An elastic mat 52 is attached to the lower surface of the top ring 51. Further, below the top ring 51, a turntable 55 having an abrasive cloth 56 pasted on the upper surface is installed. A mounting flange 182 having a concave spherical surface 182a is fixed to the top ring main body 51A. A top ring shaft 58 is disposed above the top ring 51. A drive shaft flange 184 having a concave spherical surface 184 a is fixed to the lower end of the top ring shaft 58. A spherical bearing 57 is interposed between the concave spherical surfaces 182a and 184a. Further, a space 183 is formed between the top ring main body 51A and the mounting flange 182 so that liquids such as vacuum, pressurized air, and water can be supplied to the space 183.

  The top ring shaft 58 is connected to a top ring air cylinder (not shown) fixed to the top ring head 59, and the top ring shaft 58 moves up and down by the top ring air cylinder. The semiconductor wafer 54 held on the lower end surface is pressed against the polishing pad 56 on the turntable 55.

  The top ring shaft 58 is connected to a top ring motor (not shown), and the top ring 51 is rotated by rotationally driving the top ring motor. An upper end portion of a press ring 53 provided around the top ring 51 is connected to a press ring air cylinder 72. The pressure ring air cylinder 72 is fixed to the top ring head 59. A plurality of (for example, three) pressure ring air cylinders 72 are arranged on the circumference. No means such as a key for transmitting the rotation of the top ring 51 to the pressing ring 53 is provided between the top ring 51 and the pressing ring 53. Therefore, the top ring 51 rotates around the axis of the top ring shaft 58 during polishing, but the pressing ring 53 is configured so as not to rotate with respect to its own axis.

  The top ring air cylinder and the pressure ring air cylinder 72 are each connected to a compressed air source (not shown) via a regulator (not shown). Then, by appropriately adjusting the pressing force of the guide ring with respect to the pressing force of the top ring, the distribution of the polishing pressure from the central part of the semiconductor wafer to the peripheral part and further to the outer peripheral part of the pressing ring outside the semiconductor wafer is continuous. And become uniform. Therefore, it is possible to prevent the polishing amount from being excessive or insufficient at the outer peripheral portion of the semiconductor wafer.

  In the polishing apparatus previously proposed by the present applicant in Japanese Patent Application No. 9-105252, the pressing ring 53 is supported only by the shaft of the air cylinder 72 fixed to the top ring head 59. A plurality of (for example, three) air cylinders 72 are provided at equal intervals on the circumference, but the pressing ring 53 is supported by a so-called cantilever structure that relies only on the rigidity of the shaft of the air cylinder. Since a large friction torque acts on the lower surface of the pressing ring 53, there is a problem that the pressing ring 53 has high rigidity, that is, cannot be firmly supported. Therefore, it is difficult to ensure the concentricity between the top ring and the pressing ring, the pressing ring is eccentric with respect to the top ring, and the entire circumference of the polishing cloth near the peripheral edge of the semiconductor wafer cannot be pressed uniformly. There was a problem of affecting the polishing result of the peripheral edge of the steel.

  Further, a leaf spring 67 is interposed between the top ring 51 and the pressing ring 53 in order to avoid direct contact between the top ring 51 and the pressing ring and to suppress excessive tilting of the top ring. As described above, since the rigidity of the structure for supporting the pressing ring 53 is insufficient, there is a problem that the wear of the leaf spring 67 is severe and the frequency of parts replacement is high.

  Further, in the polishing apparatus previously proposed by the present applicant, the pressing ring 53 surrounds the entire circumference of the top ring 51, and the pressing ring 53 presses the polishing cloth 56 downward during polishing of the semiconductor wafer that is the polishing object. Therefore, the inflow of the slurry-like polishing abrasive fluid supplied to the surface of the polishing cloth to the inside of the pressing ring is blocked by the pressing ring, and is actually polished between the polishing cloth and the polishing object. There was a problem that the abrasive liquid used in the process would be insufficient.

  The present invention has been made in view of the above-described circumstances, and the pressing ring has high rigidity, that is, it can sufficiently support the pressing ring, and can ensure the concentricity of the pressing ring and the top ring with high accuracy. An object is to provide a polishing apparatus.

  In order to achieve the above-described object, a polishing apparatus of the present invention has a turntable having a polishing cloth affixed to an upper surface and a top ring, and a predetermined polishing object is interposed between the turntable and the top ring. In a polishing apparatus that polishes and polishes the polishing object by pressing with a force of a pressure, a pressing ring is disposed so as to be movable up and down around a top ring that accommodates the polishing object. A pressing means for pressing the polishing cloth with a variable pressing force is provided, and the pressing ring is supported by the top ring via a bearing, and the bearing rotates relative to the pressing ring and the top ring. Supporting rotation support bearing, and vertical movement for supporting the vertical movement of the pressing ring relative to the top ring And it is characterized in that comprising the bearings.

  According to the present invention, since the pressing ring is supported by the top ring through the bearing, the pressing ring has high rigidity, that is, it can be supported sufficiently firmly, and the concentricity between the top ring and the pressing ring is ensured. can do.

  Further, according to the present invention, since the pressing ring is allowed to move up and down with respect to the top ring by the vertical movement bearing, the sliding resistance of the pressing ring during the vertical movement is extremely small, and the pressing ring smoothly moves up and down. Move.

  Furthermore, according to the present invention, since a non-contact labyrinth is installed in the entry path of foreign matter such as water to the bearing that supports the pressing ring, entry of foreign matter can be prevented and dust generation from this portion can be prevented. Can do.

  Embodiments of a polishing apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 to FIG. 3 are views showing a first embodiment of the present invention, FIG. 1 is a cross-sectional view showing an entire configuration of a polishing apparatus, and FIG. 2 is an enlarged cross-sectional view showing portions of a top ring and a pressing ring. FIG. 3 is a view taken along the line III-III in FIG.

  1 and 2, reference numeral 1 denotes a top ring. The top ring 1 includes a top ring main body 1A and a retainer ring 1B fixed to a peripheral portion of the top ring main body 1A by a bolt 31 so as to be detachable. The recess 1a for accommodating the semiconductor wafer 4 is formed by the lower surface of the top ring body 1A and the retainer ring 1B. The upper surface of the semiconductor wafer 4 is held by the lower surface of the top ring body 1A, and the outer periphery of the semiconductor wafer 4 is held by the retainer ring 1B. A pressing ring 3 is provided around the top ring main body 1A and the retainer ring 1B so as to be movable up and down.

  An elastic mat 2 is attached to the lower surface of the top ring 1. Further, below the top ring 1, a turntable 5 having an abrasive cloth 6 pasted on the upper surface is installed. A mounting flange 32 having a concave spherical surface 32a is fixed to the top ring body 1A. A top ring shaft 8 is disposed above the top ring 1. A drive shaft flange 34 having a concave spherical surface 34 a is fixed to the lower end of the top ring shaft 8. A spherical bearing 7 is interposed between the both concave spherical surfaces 32a and 34a. Further, a space 33 is formed between the top ring main body 1A and the mounting flange 32, and a liquid such as vacuum, pressurized air, or water can be supplied to the space 33. The top ring main body 1 </ b> A has a large number of communication holes 35 communicating with the space 33 and opening on the lower surface. Similarly, the elastic mat 2 has a through hole at a position facing the communication hole 35. Thus, the upper surface of the semiconductor wafer 4 (see FIG. 1) can be adsorbed by vacuum, and liquid or pressurized air can be supplied to the upper surface of the semiconductor wafer 4.

The top ring shaft 8 is connected to a top ring air cylinder 10 fixed to a top ring head 9, and the top ring shaft 8 moves up and down by the top ring air cylinder 10, and is moved to the lower end surface of the top ring 1. The held semiconductor wafer 4 is pressed against the turntable 5.
The top ring shaft 8 is connected to a rotary cylinder 11 via a key (not shown), and the rotary cylinder 11 has a timing pulley 12 on the outer periphery thereof. The timing pulley 12 is connected via a timing belt 13 to a timing pulley 15 provided in a top ring motor 14 fixed to the top ring head 9. Therefore, when the top ring motor 14 is rotationally driven, the rotary cylinder 11 and the top ring shaft 8 are integrally rotated via the timing pulley 15, the timing belt 13 and the timing pulley 12, and the top ring 1 is rotated. The top ring head 9 is supported by a top ring head shaft 16 fixedly supported by a frame (not shown).

  As shown in FIG. 2, the pressing ring 3 provided around the top ring 1 includes a first pressing ring member 3a made of alumina ceramic at the lowest position and a stainless steel located above the first pressing ring member 3a. The second and third pressing ring members 3b and 3c are made of steel. The second and third pressing ring members 3b and 3c are connected to each other by bolts (not shown), and the first pressing ring member 3a is fixed to the second pressing ring member 3b by bonding or the like. A lower end portion of the first pressing ring member 3 a is a pressing surface 3 f that presses the polishing pad 6.

  A bearing receiving flange 36 is fixed to the mounting flange 32 of the top ring 1. A press ring support bearing 37 for supporting the press ring 3 is interposed between the bearing receiving flange 36 and the press ring 3. As shown in FIGS. 2 and 3, the pressing ring support bearing 37 includes a bearing case 37a fitted to the third pressing ring member 3c and a plurality of balls arranged over the entire circumference in two rows. 37b and a retainer (not shown) for holding the ball 37b in the bearing case 37a. The upper end of the press ring support bearing 37 is pressed by a bearing press 50 fixed to the upper end of the press ring 3.

  In the present embodiment, no means such as a key for transmitting the rotation of the top ring 1 to the pressing ring 3 is provided between the top ring 1 and the pressing ring 3. Accordingly, the top ring 1 rotates around the axis of the top ring shaft 8 during polishing, but the pressing ring 3 is configured so as not to rotate with respect to its own axis, that is, the top ring 1 and the pressing ring 3 In this case, the outer peripheral surface of the bearing receiving flange 36 fixed to the top ring 1 constitutes a bearing rolling surface 36R on which the ball 37b rolls. The pressure ring support bearing 37 has a function of both a rotation support bearing and a vertical movement support bearing, and the top ring 1 and the pressure ring 3 are allowed to rotate relative to each other by the rotation support bearing function of the pressure ring support bearing 37. The pressing ring 3 is allowed to move up and down with respect to the top ring 1 by the vertical movement support bearing function of the pressing ring support bearing 37.

The lower end portion of the shaft 22 a of the air cylinder 22 for the press ring is engaged with the third press ring member 3 c of the press ring 3. The pressure ring air cylinder 22 is fixed to the top ring head 9. A plurality of (for example, three) pressure ring air cylinders 22 are arranged on the circumference. The retainer ring 1B is made of a metal such as stainless steel, and a tapered surface 1Bt inclined inward in the radial direction is formed at the outer periphery of the retainer ring 1B so that the lower side is formed thinner than the upper side. . On the other hand, a tapered surface 3t inclined radially inward is formed at a position corresponding to the tapered surface 1Bt of the retainer ring 1B on the inner peripheral portion of the pressing ring 3, and the pressing surface 3f of the pressing ring 3 is held by the top ring 1. The semiconductor wafer 4 is as close as possible to the peripheral edge of the semiconductor wafer 4.
With the configuration of the retainer ring 1 </ b> B and the pressing ring 3, the distance between the inner peripheral edge of the pressing surface 3 f of the pressing ring 3 and the peripheral edge of the semiconductor wafer 4 can be shortened. The polishing cloth 6 in the vicinity of the peripheral edge can be pressed.

As shown in FIG. 1, the top ring air cylinder 10 and the press ring air cylinder 22 are connected to a compressed air source 24 via regulators R1 and R2, respectively. Then, by adjusting the air pressure supplied to the top ring air cylinder 10 by the regulator R1, the pressing force by which the top ring 1 presses the semiconductor wafer 4 against the polishing pad 6 can be adjusted. By the regulator R2, the pressure ring air is adjusted. By adjusting the air pressure supplied to the cylinder 22, the pressing force with which the pressing ring 3 presses the polishing pad 6 can be adjusted.
An abrasive liquid supply pipe 25 is installed above the turntable 5, and the polishing abrasive liquid Q is supplied onto the polishing cloth 6 on the turntable 5 by the abrasive liquid supply pipe 25.

  In the polishing apparatus configured as described above, the semiconductor wafer 4 is held on the lower surface of the top ring 1, the top ring air cylinder 10 is operated to press the top ring 1 toward the turn table 5, and the turn table 5 rotating. The semiconductor wafer 4 is pressed against the polishing cloth 6 on the upper surface. On the other hand, by flowing the polishing abrasive liquid Q from the abrasive liquid supply pipe 25, the polishing abrasive liquid Q is held on the polishing cloth 6, and polishing is performed between the surface (lower surface) of the semiconductor wafer 4 to be polished and the polishing cloth 6. Polishing is performed in the state where the abrasive liquid Q is present.

The semiconductor wafer 4 is polished by appropriately adjusting the pressing force of the pressing ring 3 to the polishing pad 6 by the pressing ring air cylinder 22 according to the pressing force of the top ring 1 by the top ring air cylinder 10. By the regulator R1 during polishing can change the pressing force F ₁ which the top ring 1 to press the semiconductor wafer 4 to the polishing cloth 6 on the turntable 5, the pressing force F ₂ which is pressure ring 3 presses the polishing cloth 6 by the regulator R2 Can be changed (see FIG. 1). Therefore, during the polishing, the pressing force F ₂ by which the pressing ring 3 presses the polishing cloth 6 can be changed according to the pressing force F ₁ by which the top ring 1 presses the semiconductor wafer 4 against the polishing cloth 6. By appropriately adjusting the pressing force F ₂ against the pressing force F _1, the peripheral edge portion, and further distribution of polishing pressure to the outer circumferential portion of the pressure ring 3 is continuously on the outside of the semiconductor wafer 4 from the center of the semiconductor wafer 4 And become uniform. Therefore, excessive or insufficient polishing amount at the peripheral edge of the semiconductor wafer 4 can be prevented.

If you want to reduce the number or reverse intentionally polishing amount than the inner side in the also the periphery of the semiconductor wafer 4, the optimum value based on the pressing force F ₂ of the pressing ring with the pressing force F ₁ of the top ring By selecting, the polishing amount of the peripheral edge of the semiconductor wafer 4 can be intentionally increased or decreased.

  In the present embodiment, since the pressing ring 3 is supported by the top ring 1 via the pressing ring support bearing 37, the pressing ring 3 has high rigidity, that is, is sufficiently firmly supported. Further, since the pressing ring 3 is allowed to move up and down with respect to the top ring 1 by the vertical movement support bearing function of the pressing ring support bearing 37, the sliding resistance of the pressing ring 3 during the vertical movement is extremely small. 3 moves up and down smoothly.

  Further, since the pressing ring 3 is supported by the pressing ring support bearing 37 disposed concentrically with the axis of the top ring 1, the concentricity between the pressing ring 3 and the top ring 1 can be ensured with high accuracy. As a result, the distance between the pressing ring 3 and the top ring 1 and thus the distance between the inner peripheral edge of the pressing ring 3 and the outer peripheral edge of the semiconductor wafer 4 supported by the top ring 1 can be kept uniform over the entire periphery. . Further, this makes it possible to make the distance between the pressing ring 3 and the top ring 1, that is, the semiconductor wafer 4, smaller than that of the conventional case, that is, more than the case where the taper surfaces of the retainer ring and the pressing ring are provided. Thus, stable performance and ease of control can be realized. Specifically, since it can be uniformly polished to a position closer to the periphery of the polishing surface of the wafer, the number of semiconductor device products obtained from one wafer increases, and the operating conditions such as the pressing force of the pressing ring during polishing can be reduced. Responsiveness when changing is improved.

  Further, in the polishing apparatus previously proposed by the applicant shown in FIG. 14, a leaf spring for suppressing the tilting of the top ring is interposed between the pressing ring and the top ring. In the configuration, the possibility that the pressing ring is in direct contact with the top ring is reduced, and the possibility that the top ring is tilted excessively is reduced. Since this member is handled as a consumable member, the cost of the consumable member is reduced as a result.

4 and 5 are diagrams showing a second embodiment of the present invention. In the second embodiment, members having the same functions or functions as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.
In the present embodiment, the rotation support bearing function and the vertical movement support bearing function of the pressing ring support bearing 37 in the first embodiment are divided so that the respective functions are shared by the individual bearings 38 and 39. Is. That is, a bearing receiving ring 40 is provided on the outer peripheral portion of the mounting flange 32 of the top ring 1 via a rotation support bearing 38, and a vertical movement support bearing 39 is provided between the bearing receiving ring 40 and the pressing ring 3. It is intervened. The rotation support bearing 38 is a normal radial bearing. As shown in FIGS. 4 and 5, the vertical movement support bearings 39 are installed at three locations on the circumference, and each vertical movement support bearing 39 is a plate having a bearing rolling surface 39 </ b> R fixed to the pressing ring 3. And a bearing case 39c that accommodates the roller 39b. The bearing case 39 c is fixed to the bearing receiving ring 40, and a bearing holder 69 is fixed to the bearing receiving ring 40.

A pressing ring stopper 70 is fixed to the upper end portion of the pressing ring 3, and a cover 71 is fixed to the upper end portion of the mounting flange 32. Three labyrinths 75, 76, 77 are formed so as to surround the rotation support bearing 38 and the vertical movement support bearing 39. That is, a labyrinth 75 is formed between the bearing retainer 69, the pressing ring stopper 70, and the cover 71, and a labyrinth 76 is formed between the bearing receiving ring 40 and the mounting flange 32. A labyrinth 77 is formed between the pressing ring member 3c and the retainer 1B.
According to the present embodiment shown in FIGS. 4 and 5, it is possible to bring the bearing support position closer to the polishing surface than in the first embodiment. As a result, the support stability of the pressing ring 3 can be further ensured.

  In the first embodiment, since the two motions are received by one bearing, the ball strikes on the motion surface of the ball, that is, the rolling surface so that the ball moves in two directions at the same time. Therefore, depending on the hardness of the rolling surface, there is a possibility that greater wear will occur at the contact surface and the life of the bearing will be shortened. In the present embodiment, the relative rotation between the top ring 1 and the pressing ring 3 is supported by the rotation support bearing 38, and the vertical movement of the pressing ring 3 with respect to the top ring 1 is supported by the vertical movement support bearing 39. That is, it is possible to give only one direction of movement to one bearing, and it is possible to contribute to the improvement of the life of the bearing by making the rolling contact line contact.

  When adopting the above-described structure, it is not preferable that foreign matters enter the bearing installation portion, for example, liquid such as water or polishing liquid or solid matter such as polishing waste. Therefore, it is necessary to prevent the liquid or solid matter from entering the periphery of the bearing. As a means for this, the periphery is mechanically sealed with a contact-type seal or covered with a structure such as a labyrinth. A method is conceivable. For example, when mechanically sealed, there is a considerable amount of wear at the contact portion, and the seal itself may become a consumable member. Wearing also leads to the generation of foreign matter due to wear, which itself can be a source of foreign matter. On the other hand, since the labyrinth structure as shown in FIG. 4 is non-contact, there is no concern as described above. Furthermore, by arranging a plurality of labyrinths 75, 76, 77, it is possible to improve the accuracy of preventing foreign substances from entering. In addition, it is not preferable for foreign matter to enter the polishing surface, and the use of the labyrinth structure can also be expected to prevent the foreign matter generated in the portion above the polishing surface from falling. Other functions and effects in the second embodiment are the same as those in the first embodiment.

  FIG. 6 is a cross-sectional view of an essential part showing an improved structure of the polishing apparatus shown in FIGS. In the example shown in FIG. 6, an inlay portion IN is formed in the upper end outer peripheral portion of the top ring main body 1A and the lower end outer peripheral portion of the mounting flange 32, and the top ring main body 1A and the mounting flange 32 are positioned by fitting. . Therefore, the centering of the top ring main body 1A and the mounting flange 32 is performed only by fitting these two members, and the assemblability is improved. Further, an O-ring 80 that seals a space 33 for supplying vacuum or pressurized air formed between the top ring body 1A and the mounting flange 32 is provided inside the bolt 81 that fixes the mounting flange 32 and the top ring 1A. Provided. Therefore, it is not necessary to provide a washer having a sealing property at the bolt 81 portion.

  On the other hand, in the press ring 3, a cleaning water supply pipe 82 is fixed to the upper part of the third pressing ring member 3c, and a cleaning water discharge port 83 is formed at the lower end. An annular channel 84 is formed at the upper end of the second pressing ring member 3b that holds the first pressing ring member 3a. The annular channel 84 communicates with the inner circumferential surface of the second pressing ring member 3b via a plurality of communication passages 85 provided at predetermined intervals in the circumferential direction. The second pressing ring member 3b has a plurality of drain holes 86 formed in the lower portion at intervals in the circumferential direction. The inner peripheral surface of the second pressing ring member 3b is recessed inward, and a relatively wide space 88 is formed between the retainer ring 1B and the pressing ring 3. Further, a resin coating 89 made of polytetrafluoroethylene is formed on the inner and outer peripheral surfaces of the second pressing ring member 3b.

  In the above-described configuration of the pressing ring 3, the slurry-like polishing abrasive fluid that has entered between the guide ring 1 </ b> B and the pressing ring 3 flows out of the pressing ring 3 from the space 88 through the drain hole 86. Therefore, it is possible to prevent the slurry-like polishing abrasive liquid from entering the upper portion of the guide ring 1B.

  In addition, by appropriately supplying cleaning water from the cleaning water supply pipe 82, the cleaning water passes through the cleaning water discharge port 83, the annular channel 84, and the communication path 85, and a space 88 between the guide ring 1 </ b> B and the pressing ring 3. Flow into. Thereafter, the cleaning water takes a flow path that flows out from the gap 91 between the guide ring 1B and the pressing ring 3 and a system path that flows out of the pressing ring 3 through the drain hole 86, and thereby the guide ring 1B and the pressing ring. 3 are washed. In addition, since the gap 90 is formed at the outer peripheral connection portion between the second pressing ring member 3b and the third pressing ring member 3c, the cleaning water in the annular flow path 84 passes through the gap 90 and the pressing ring 3. Therefore, the outer peripheral surface of the pressing ring 3 is cleaned. Further, since the resin coating 89 is applied to the inner and outer surfaces of the second pressing ring member 3b of the pressing ring 3, the slurry-like polishing abrasive liquid is difficult to adhere, and even if it adheres, the polishing abrasive is supplied by supplying cleaning water. The liquid can be easily removed.

  As described above, according to the present invention, since the pressing ring is supported by the top ring via the bearing, the pressing ring has high rigidity, that is, is sufficiently firmly supported. In addition, since the pressing ring is allowed to move up and down with respect to the top ring by the vertical movement support bearing function of the bearing or a dedicated vertical movement support bearing, the sliding resistance of the pressure ring during vertical movement is extremely small. Moves up and down smoothly.

  Further, since the pressing ring is supported by a bearing arranged concentrically with the axis of the top ring, the concentricity between the pressing ring and the top ring can be ensured with high accuracy. As a result, the distance between the pressing ring and the top ring, and hence the distance between the inner peripheral edge of the pressing ring and the outer peripheral edge of the semiconductor wafer supported by the top ring can be kept uniform over the entire periphery. Furthermore, since this interval can be kept uniform, the interval can be set smaller, and the polishing performance is improved.

  In addition, according to the present invention, since a non-contact labyrinth is installed in the entry path of foreign matters such as water to the bearing that supports the pressing ring, it is possible to prevent the entry of foreign matters and to prevent dust generation from this portion. Can do.

  Next, a third embodiment of the polishing apparatus according to the present invention will be described with reference to FIGS. 7 is an enlarged cross-sectional view showing portions of the top ring and the pressing ring, FIG. 8A is an enlarged cross-sectional view of the main part of FIG. 7, and FIG. 8B is a cross-sectional view taken along line VIII-VIII of FIG.

  In FIG. 7, reference numeral 1 denotes a top ring. The top ring 1 includes a top ring main body 1 </ b> A and a retainer ring 1 </ b> B that is detachably fixed to an outer peripheral portion of the top ring main body 1 </ b> A by a bolt 31. The concave portion 1a for housing the upper ring is formed by the lower surface of the top ring body 1A and the retainer ring 1B. The upper surface of the semiconductor wafer 4 (see FIG. 1) is held by the lower surface of the top ring body 1A, and the outer peripheral portion of the semiconductor wafer 4 is held by the retainer ring 1B. A pressing ring 3 is provided around the top ring main body 1A and the retainer ring 1B so as to be movable up and down. Further, a leaf spring 17 having a substantially U-shaped cross section for suppressing excessive tilting of the top ring 1 is interposed between the pressing ring 3 and the top ring 1.

  A mounting flange 32 having a concave spherical surface 32a is fixed to the top ring body 1A. A top ring shaft 8 is disposed above the top ring 1. A drive shaft flange 34 having a concave spherical surface 34 a is fixed to the lower end of the top ring shaft 8. A spherical bearing 7 is interposed between the both concave spherical surfaces 32a and 34a. Further, a space 33 is formed between the top ring main body 1A and the mounting flange 32, and a liquid such as vacuum, pressurized air, or water can be supplied to the space 33. The top ring main body 1 </ b> A has a large number of communication holes 35 communicating with the space 33 and opening on the lower surface. Similarly, the elastic mat 2 has an opening at a position facing the communication hole 35. Thus, the upper surface of the semiconductor wafer 4 (see FIG. 1) can be adsorbed by vacuum, and liquid or pressurized air can be supplied to the upper surface of the semiconductor wafer 4.

  As shown in FIG. 7 and FIG. 8A, the pressing ring 3 provided around the top ring 1 includes a first pressing ring member 3a made of alumina ceramic at the lowest position and an upper side of the first pressing ring member 3a. The second and third pressing ring members 3b and 3c made of stainless steel and the fourth pressing ring member 3d made of stainless steel at the uppermost position are formed. The 2nd-4th press ring members 3b-3d are mutually connected by the volt | bolt, and the 1st press ring member 3a is being fixed to the 2nd press ring member 3b by adhesion | attachment etc. The lower end portion of the first pressing ring member 3a protrudes downward only on the inner peripheral side to form a protruding portion 3e, and only the lower end surface of the protruding portion 3e becomes a pressing surface 3f that presses the polishing pad 6. Yes.

  A radial width or thickness t of the pressing surface 3f is set to 2 mm to 6 mm. The upper end portion of the pressing ring 3 is connected to the pressing ring air cylinder 22. The pressure ring air cylinder 22 is fixed to the top ring head 9. A plurality of (for example, three) pressure ring air cylinders 22 are arranged on the circumference. The retainer ring 1B is made of a metal such as stainless steel, and a tapered surface 1Bt inclined inward in the radial direction is formed at the outer periphery of the retainer ring 1B so that the lower side is formed thinner than the upper side. . On the other hand, a tapered surface 3t inclined inward in the radial direction is formed at a position corresponding to the tapered surface of the retainer ring 1B on the inner peripheral portion of the pressing ring 3, and the pressing surface 3f of the pressing ring 3 is held by the top ring 1. It is as close as possible to the peripheral edge of the semiconductor wafer 4.

  With the configuration of the retainer ring 1 </ b> B and the pressing ring 3, the distance between the inner peripheral edge of the pressing surface 3 f of the pressing ring 3 and the peripheral edge of the semiconductor wafer 4 can be shortened. The polishing cloth 6 in the vicinity of the peripheral edge can be pressed. Therefore, it is possible to prevent the peripheral portion of the semiconductor wafer 4 from being overpolished. The retainer ring 1B is provided with a resin coating 18 on its lower inner peripheral surface and lower end surface as shown by the thick line in FIG. 8A. The resin coating 18 is preferably PEEK (polyetherketone), polytetrafluoroethylene, polyvinyl chloride or the like, and the film thickness is suitably within 100 microns. Since the resin coating 18 is applied to the metal retainer ring 1B, metal contamination of the semiconductor wafer 4 can be prevented.

  In the present embodiment, no means such as a key for transmitting the rotation of the top ring 1 to the pressing ring 3 is provided between the top ring 1 and the pressing ring 3. Accordingly, the top ring 1 rotates around the axis of the top ring shaft 8 during polishing, but the pressing ring 3 is configured so as not to rotate with respect to its own axis. For this reason, the rotational force of the top ring 1 is not transmitted to the pressing ring 3, so that the rotational load on the top ring shaft 8 is reduced. Further, since the pressing ring 3 can be directly operated by the pressing ring air cylinder 22 fixed to the top ring head 9, the structure of the apparatus is simplified.

  Further, as shown in FIGS. 7, 8A, and 8B, the peripheral wall of the second pressing ring member 3b of the pressing ring 3 has a plurality of (for example, six) abrasive supply holes 3m that penetrate the peripheral wall in a radial manner. Is formed. As shown in FIG. 8B, the abrasive liquid is supplied to a plurality of (for example, three) openings located upstream of the rotation direction R of the turntable 5 among the plurality of abrasive liquid supply holes 3m. Each branch pipe 101 of the tube 100 is connected. The abrasive liquid supply tube 100 is connected to an abrasive liquid supply source 102. The opening of the other abrasive liquid supply hole 3 m is closed by a plug member 103. The abrasive liquid supply tube 100 is provided with a pump 104 that controls the flow rate of the abrasive liquid to be supplied, and an on-off valve 105 a that is located upstream of the pump 104 and starts and stops the supply of the abrasive liquid. The abrasive liquid supply hole 3m, the connector 107a, the branch pipe 101, the abrasive liquid supply tube 100, the pump 104, and the abrasive liquid supply source 102 constitute an abrasive liquid supply means, and can supply the abrasive liquid to the inside of the pressing ring 3. It is like that. Since the pressing ring 3 is configured to be non-rotating, the abrasive liquid can be easily supplied from the abrasive liquid supply source 102 to the abrasive liquid supply hole 3m without using a rotary joint or the like.

  By supplying the abrasive fluid from the abrasive fluid supply means to the inside of the press ring 3, the polishing ring abrasive slurry is prevented from flowing into the press ring 3 by the press ring 3 during polishing of the semiconductor wafer 4. However, the shortage of the abrasive liquid used for polishing can be eliminated. Therefore, the polishing of the polishing object is smoothly performed under a sufficient abrasive liquid.

  A cleaning liquid supply tube 108a is connected between the on-off valve 105a of the abrasive liquid supply tube 100 and the pump 104, and this tube 108a is connected to a cleaning liquid supply source 109 to constitute a cleaning means. An opening / closing valve 105b is also interposed in the cleaning liquid supply tube 108a. As a result, by opening the on-off valve 105b and supplying the cleaning liquid from the cleaning means to the abrasive liquid supply tube 100 and the abrasive liquid supply hole 3m of the abrasive liquid supply means, the abrasive liquid adhering to the inside can be washed away.

  Further, between the second pressing ring member 3b and the third pressing ring member 3c of the pressing ring 3, FIG. 9A (enlarged sectional view of the main part in FIG. 7) and FIG. 9B (sectional view taken along the line IX-IX in FIG. 9A). As shown in FIG. 3, a cleaning liquid flow path 3i composed of a circumferential groove formed over the entire circumference is provided on the upper surface of the second pressing ring member 3b. The second pressing ring member 3b is radially provided with a cleaning liquid supply hole 3j that communicates with the cleaning liquid flow path 3i and opens to the outer peripheral surface, and a cleaning liquid discharge hole 3k that communicates with the cleaning liquid flow path 3i and opens to the inner peripheral surface. A plurality are provided. A cleaning liquid supply tube 108b is connected to the opening of the cleaning liquid supply hole 3j via a connector 107b. The cleaning liquid supply tube 108b is also connected to the cleaning liquid supply source 109 through the on-off valve 106 in the same manner as the above-described cleaning liquid supply tube 108a. The cleaning liquid discharge hole 3k, the cleaning liquid flow path 3i, the cleaning liquid supply hole 3j, the connector 107b, the cleaning liquid supply tube 108b, and the cleaning liquid supply source 109 constitute a cleaning liquid supply means. Since the pressing ring 3 is configured to be non-rotating, it is possible to easily supply the cleaning liquid from the cleaning liquid supply source 109 to the cleaning liquid flow path 3i and discharge the cleaning liquid from the cleaning liquid discharge hole 3k without using a rotary joint or the like.

  By appropriately supplying the cleaning liquid from the cleaning liquid supply means to the gap between the pressing ring 3 and the retainer ring 1B of the top ring 1, the slurry-like polishing abrasive liquid that has entered the gap can be washed away. Therefore, the polishing abrasive liquid does not adhere between the pressing ring 3 and the retainer ring 1B of the top ring 1, and the smooth movement of the pressing ring 3 can be ensured.

  The pressing ring 3 is formed with a plurality of vent holes 3v for discharging gas such as air accumulated in the gap between the pressing ring 3 and the retainer ring 1B of the top ring 1 (see FIG. 8A). Therefore, since the gas is not trapped (filled) in the gap between the pressing ring 3 and the retainer ring 1B of the top ring 1, the pressing ring 3 can be moved up and down smoothly. Therefore, at the start of polishing, the pressing ring 3 can contact the polishing cloth 6 at an optimal timing and press it with a desired pressing force.

  10A is a perspective view showing a part of the pressing ring, and FIG. 10B is a view taken in the direction of arrow X in FIG. 10A. As shown in FIGS. 10A and 10B, the pressure ring 3 includes a polishing liquid supply hole 3m, a polishing liquid supply groove 3p extending downward from the opening end of the polishing liquid supply hole 3m, a cleaning liquid discharge hole 3k, and a cleaning liquid supply flow path 3i. Is formed. The abrasive liquid supplied to the abrasive liquid supply hole 3m flows down along the abrasive liquid guide groove 3p and reaches the polishing pad 6.

  11A and 11B are views showing another embodiment of the pressing ring, FIG. 11A is a perspective view showing a part of the pressing ring, and FIG. 11B is a view taken along arrow XI in FIG. 11A. The inner circumferential surface of the pressing ring 3 has a smooth circumferential surface with no steps. The pressing ring 3 is provided with a polishing liquid supply hole 3m, a cleaning liquid discharge hole 3k, and a cleaning liquid flow path 3i, as in the embodiment of FIGS. 10A and 10B. A cleaning liquid guide groove 3n that connects the opening end of the cleaning liquid discharge hole 3k and the opening end of the abrasive liquid supply hole 3m, and an opening end of the abrasive liquid supply hole 3m are provided on the inner peripheral surface of the pressing ring 3. A polishing liquid guide groove 3p is formed extending in the direction. Therefore, the abrasive liquid supplied to the abrasive liquid supply hole 3m flows down along the abrasive liquid guide groove 3p and reaches the polishing pad 6. The abrasive liquid adhering to the abrasive liquid supply hole 3m and the abrasive liquid guide groove 3p is supplied to the abrasive liquid supply hole 3m by the cleaning means and flows along the abrasive liquid guide groove 3p, and the cleaning liquid is discharged by the cleaning liquid supply means. Cleaning is performed with both of the cleaning liquid discharged from the hole 3k and flowing along the abrasive liquid guide groove 3p from the cleaning liquid guide groove 3n through the abrasive liquid supply hole 3m.

  In the polishing apparatus configured as described above, the semiconductor wafer 4 is held on the lower surface of the top ring 1, the top ring air cylinder 10 is operated to press the top ring 1 toward the turn table 5, and the turn table 5 rotating. The semiconductor wafer 4 is pressed against the polishing cloth 6 on the upper surface. On the other hand, by flowing the polishing abrasive liquid Q from the abrasive liquid supply nozzle 25, the polishing abrasive liquid Q is held on the polishing cloth 6, and at the same time, the abrasive liquid is supplied to the inside of the pressing ring 3 by the abrasive liquid supply means. Thus, polishing is performed in a state where a sufficient polishing abrasive liquid Q exists between the surface (lower surface) of the semiconductor wafer 4 to be polished and the polishing pad 6.

The semiconductor wafer 4 is polished by appropriately adjusting the pressing force of the pressing ring 3 to the polishing pad 6 by the pressing ring air cylinder 22 according to the pressing force of the top ring 1 by the top ring air cylinder 10. By the regulator R1 during polishing can change the pressing force F ₁ which the top ring 1 to press the semiconductor wafer 4 to the polishing cloth 6 on the turntable 5, the pressing force F ₂ which is pressure ring 3 presses the polishing cloth 6 by the regulator R2 Can be changed (see FIG. 1). Therefore, during the polishing, the pressing force F ₂ by which the pressing ring 3 presses the polishing cloth 6 can be changed according to the pressing force F ₁ by which the top ring 1 presses the semiconductor wafer 4 against the polishing cloth 6. By appropriately adjusting the pressing force F ₂ against the pressing force F _1, the peripheral edge portion, and further distribution of polishing pressure to the outer circumferential portion of the pressure ring 3 is continuously on the outside of the semiconductor wafer 4 from the center of the semiconductor wafer 4 And become uniform. Therefore, excessive or insufficient polishing amount at the peripheral edge of the semiconductor wafer 4 can be prevented.

Further, when it is desired to intentionally increase the polishing amount at the peripheral edge of the semiconductor wafer 4 from the inner side, or conversely, reduce the pressing force F ₂ of the pressing ring 3 based on the pressing force F ₁ of the top ring 1. By selecting the value, the polishing amount of the peripheral edge of the semiconductor wafer 4 can be intentionally increased or decreased.

  For example, before performing the next polishing after the polishing of the semiconductor wafer 4, the cleaning liquid is supplied to the gap between the pressing ring 3 and the top ring 1 and enters the gap between the pressing ring 3 and the top ring 1. The slurry-like polishing abrasive liquid is washed away, and at the same time, the cleaning liquid is supplied to the abrasive liquid supply tube 100 and the abrasive liquid supply hole 3m of the abrasive liquid supply means via the cleaning means, and the abrasive liquid adhering thereto is washed away.

  According to this embodiment, since the means for supplying the abrasive liquid is provided inside the pressing ring 3, the slurry-like polishing abrasive liquid flows into the pressing ring 3 by the pressing ring 3 during polishing of the semiconductor wafer 4. Even if it is interrupted, by supplying the abrasive liquid to the inside of the pressing ring 3, the shortage of the abrasive liquid used for polishing can be eliminated. Therefore, the polishing of the polishing object is smoothly performed under a sufficient abrasive liquid. Even in the case of the large-diameter semiconductor wafer 4, a sufficient amount of abrasive liquid is ensured.

  Moreover, according to the present Example, the retainer ring 1B and the press ring 3 can be selected from materials that are optimal. The retainer ring 1B can be selected from materials having a relatively soft surface by means such as applying a resin coating 18 to a metal because the inner peripheral surface thereof is in contact with the semiconductor wafer 4 and the lower end thereof is not in contact with the polishing pad 6. . This is because if a hard material is used, the semiconductor wafer 4 may be damaged during polishing. Even if the retainer ring 1B and the pressing ring 3 come into contact with each other, since they are in contact with each other through the resin coating 18, there is no contact between the metals, and the relative movement between the pressing ring 3 and the retaining ring 1B (vertical movement and rotational movement). ) Is carried out smoothly.

  Further, since the first pressing ring 3a is not in contact with the semiconductor wafer 4 and is in contact with the polishing cloth 6, the first pressing ring 3a may be selected from a material having high hardness such as alumina ceramic and high wear resistance and a low friction coefficient. it can. It is desirable that the pressure ring has little wear and frictional resistance with the polishing cloth, and wear powder of the pressure ring does not adversely affect the semiconductor devices on the semiconductor wafer 4. Since the first pressing ring 3a does not come into direct contact with the semiconductor wafer 4 as described above, there is no restriction from this surface, so an alumina ceramic that is the optimum material that satisfies the above requirements should be selected. Can do. In addition to the alumina ceramic, the material of the pressing ring may be a ceramic such as silicon carbide (SiC) or zirconia.

  In the present embodiment, an example is shown in which the pressing ring 3 is configured to be non-rotating, but the pressing ring is configured to be rotatable and the abrasive fluid is supplied to the inside of the pressing ring via a rotary joint. Also good.

  As described above, according to the present invention, since the means for supplying the abrasive liquid is provided on the inner side of the pressing ring, the slurry-like polishing abrasive liquid is prevented from flowing into the inner side of the pressing ring by the pressing ring during polishing. However, by supplying the abrasive liquid directly to the polishing portion inside the pressing ring, the shortage of the abrasive liquid used for polishing can be eliminated. Therefore, the polishing of the polishing object is smoothly performed under a sufficient abrasive liquid.

  The present invention relates to a polishing apparatus for polishing a polishing target such as a semiconductor wafer in a flat and mirror-like manner, and can be used in a semiconductor device manufacturing process.

FIG. 1 is a cross-sectional view showing the overall configuration of a first embodiment of a polishing apparatus according to the present invention. FIG. 2 is a cross-sectional view showing the main configuration of the first embodiment of the polishing apparatus according to the present invention. 3 is a view taken along the line III-III in FIG. FIG. 4 is a cross-sectional view showing the main configuration of a polishing apparatus according to a second embodiment of the present invention. FIG. 5 is a view taken along line VV in FIG. FIG. 6 is a cross-sectional view of an essential part showing an improved structure of the polishing apparatus shown in FIGS. FIG. 7 is a cross-sectional view showing the main configuration of a third embodiment of the polishing apparatus according to the present invention. FIG. 8A is an enlarged cross-sectional view of a main part of FIG. 8B is a cross-sectional view taken along line VIII-VIII in FIG. 8A. 9A is an enlarged cross-sectional view of a main part of FIG. 9B is a cross-sectional view taken along line IX-IX in FIG. 9A. FIG. 10A is a perspective view showing a part of the pressing ring. FIG. 10B is a view on arrow X of FIG. 10A. FIG. 11A is a perspective view showing a part of the pressing ring. FIG. 11B is a view taken along arrow XI in FIG. 11A. FIG. 12 is a sectional view showing a schematic structure of a conventional polishing apparatus. FIG. 13 is an enlarged sectional view showing a state of a semiconductor wafer, a polishing pad and an elastic mat in a conventional polishing apparatus. FIG. 14 is a diagram showing a main part of an example of the polishing apparatus previously proposed by the applicant.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Top ring 1A Top ring main body 1B Retainer ring 2 Elastic mat 3 Press ring 3a 1st press ring member 3b 2nd press ring member 3c 3rd press ring member 3d 4th press ring member 3f Press surface 4 Semiconductor wafer 5 Turntable 6 Polishing cloth 7 Ball bearing 8 Top ring shaft 9 Top ring head 10 Top ring air cylinder 11 Rotating cylinders 12, 15 Timing pulley 14 Top ring motor 16 Top ring head shaft 17 Plate spring 18 Resin coating 22 Press ring air cylinder 24 Compressed air source 25 Abrasive liquid supply pipe 31 Bolt 32 Mounting flange 32a, 34a Concave spherical surface 33 Space 34 Drive shaft flange 35 Communication hole 36 Bearing receiving flange 37 Press ring support bearing 37b Ball 37a Scan 38 rotation support bearing 39 move up and down the support bearing 40 bearing receiving ring 50,69 bearing retainer 70 pressing ring stopper 71 cover 75, 76 Labyrinth

Claims (3)

It has a turntable and a top ring with a polishing cloth affixed to the upper surface, and polishes the polishing object by pressing it with a predetermined force with a polishing object interposed between the turntable and the top ring, In a flat and mirror polishing apparatus,
A pressing ring is disposed around a top ring that accommodates the polishing object, and is provided with pressing means that presses the pressing ring against a polishing cloth with a variable pressing force. The pressing ring is interposed via a bearing. Configured to be supported by the top ring,
The polishing apparatus according to claim 1, wherein the bearing includes a rotation support bearing that supports relative rotation of the pressing ring and the top ring, and a vertical movement bearing that supports vertical movement of the pressing ring with respect to the top ring.   The polishing apparatus according to claim 1, wherein a labyrinth is provided in an entry path of foreign matter into the bearing in order to prevent foreign matters such as water from entering the bearing.   The polishing apparatus according to claim 2, further comprising a cleaning liquid supply unit that supplies a cleaning liquid to a gap between the pressing ring and the top ring.

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