JP2017001111A - Polishing pad and CMP polishing method - Google Patents

Abstract

An object of the present invention is to prevent a polishing surface of a polishing pad from being cut out by a wafer during polishing.
A polishing pad (46) is formed using a thermoplastic resin and includes a groove (62) intersecting the polishing surface. The groove is a groove side surface facing the polishing surface (61) at a predetermined depth. (63) and a groove bottom surface (64) connected to the groove side surface facing each other, and a chamfering (65) which is thermoplastically deformed is provided at a connection portion between the polished surface and the groove side surface. Thereby, it can suppress that the grinding | polishing surface of a polishing pad is notched by the angle | corner (29) of a chip | tip (C).
[Selection] Figure 3

Description

  The present invention relates to a polishing pad and a CMP polishing method for polishing a wafer while supplying a slurry.

  As a CMP (Chemical Mechanical Polishing) polishing pad, a porous type, a non-woven yarn type, and a suede type are known. The suede type polishing pad is soft and has a large number of holes through which the slurry enters the polishing surface, and is suitable for polishing the wafer to a mirror surface. As this type of suede-type polishing pad, a polishing pad in which a groove for assisting the supply of slurry is formed on a polishing surface is known (see, for example, Patent Document 1). Grooves are formed on the polishing surface of the polishing pad described in Patent Document 1 by cutting, and the slurry is spread over the entire polishing surface through the grooves, so that the wafer is polished well by the polishing pad.

JP 2010-115717 A

  However, when the divided wafer chip is polished using the polishing pad described in Patent Document 1, the polishing surface is notched because the corner or upper side of the chip hits the groove side surface or corner of the polishing pad. There was a problem of consuming the polishing pad. In this case, if the polishing surface is notched into the chip to generate polishing scraps, the polishing scraps may adhere to the chips, and it has been difficult to remove the polishing scraps attached to the chips by subsequent cleaning or the like. . Further, if the polished surface is cut into chips and the flatness of the polished surface is disturbed, the wafer chip cannot be properly polished.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a polishing pad and a CMP polishing method that suppress the cutting of the polishing surface of the polishing pad by a wafer during polishing.

  The polishing pad of the present invention is a polishing pad for polishing a wafer, and is provided with a groove that is formed using a thermoplastic resin and intersects the polishing surface, and the groove is a groove facing the polishing surface at a predetermined depth. A groove bottom surface connected to the groove side surface facing the side surface is provided, and a chamfer is provided at a connection portion between the polishing surface and the groove side surface.

  According to this configuration, since the intersecting grooves are formed on the polishing surface, the slurry passes through the grooves over the entire polishing surface, and the wafer can be polished well. Further, no corner is formed between the polishing surface of the polishing pad and the side surface of the groove, which is easily cut at the corner of the wafer, and the contact with the corner of the wafer is reduced by chamfering. Moreover, since the polishing pad is formed using a thermoplastic resin, the groove and the chamfer can be formed by thermoplastic deformation of the polishing pad. In the thermoplastic deformation, the groove of the polishing pad and the hole on the chamfered surface are crushed and the wafer is hardly caught. Therefore, the polishing surface of the polishing pad can be prevented from being cut out by the wafer, the flatness of the polishing surface can be maintained, and polishing scraps of the polishing pad can be reduced to suppress adhesion to the wafer.

  In the CMP polishing method of the present invention, a protective tape is attached to one surface of a wafer provided with a division line, and a holding table holds the wafer divided along the division line via the protective tape. A polishing method for supplying a slurry to a polishing pad and polishing the wafer using the polishing pad, wherein the wafer divided by the suction of the protective tape is sucked by the holding table A holding step for holding, and a CMP polishing step for polishing the divided wafer using the polishing pad by supplying slurry after the holding step.

  According to the present invention, since the chamfer is provided at the connecting portion between the polishing surface of the polishing pad formed using the thermoplastic resin and the side surface of the groove, the polishing surface of the polishing pad is notched by the wafer during polishing. Can be suppressed.

1 is a perspective view of a CMP polishing apparatus according to an embodiment. It is explanatory drawing of the grinding | polishing process by the polishing pad in which the groove | channel was formed by cutting. It is explanatory drawing which shows the polishing pad which concerns on this Embodiment. It is explanatory drawing of the polishing process using the polishing pad which concerns on this Embodiment. It is explanatory drawing of the CMP grinding | polishing method which concerns on this Embodiment. It is explanatory drawing of the manufacturing method of the polishing pad which concerns on this Embodiment.

  Hereinafter, a CMP polishing apparatus will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a CMP polishing apparatus according to the present embodiment. Note that the CMP polishing apparatus according to the present embodiment is not limited to a polishing-dedicated apparatus as shown in FIG. 1, and is, for example, a fully automatic type in which a series of processes such as grinding, polishing, and cleaning are performed automatically. It may be incorporated in the processing apparatus.

  As shown in FIG. 1, the CMP polishing apparatus 1 causes the slurry to enter between the wafer W on the holding table 21 and the polishing pad 46, and polishes the wafer W by chemical mechanical polishing (CMP). It is configured. The wafer W provided with the division line is divided into a plurality of chips C along the division line, and the protective tape T is attached to one surface of the wafer W. The wafer W may be a semiconductor wafer in which semiconductor devices such as IC and LSI are formed on a semiconductor substrate, or an optical device wafer in which optical devices such as LEDs are formed on an inorganic material substrate.

  A rectangular opening extending in the X-axis direction is formed on the upper surface of the base 11 of the CMP polishing apparatus 1, and this opening is covered with a table cover 12 that can move together with the holding table 21 and a bellows-shaped waterproof cover 13. It has been broken. Below the waterproof cover 13, a moving unit 24 that moves the holding table 21 in the X-axis direction and a rotating unit 22 that continuously rotates the holding table 21 are provided. On the surface of the holding table 21, a holding surface 23 that holds the divided wafer W via the protective tape T is formed by a porous porous material. The holding surface 23 is connected to a suction source (not shown) through a flow path in the holding table 21.

  The moving means 24 has a pair of guide rails 51 arranged on the base 11 and parallel to the X-axis direction, and a motor-driven X-axis table 52 slidably installed on the pair of guide rails 51. Yes. A nut portion (not shown) is formed on the back side of the X-axis table 52, and a ball screw 53 is screwed to the nut portion. Then, when the drive motor 54 connected to one end of the ball screw 53 is rotationally driven, the holding table 21 is moved along the pair of guide rails 51 in the X-axis direction. The rotating means 22 is provided on the X-axis table 52, and supports the holding table 21 so as to be rotatable around the Z-axis.

  The column 14 on the base 11 is provided with a processing feed means 31 for processing and feeding the polishing means 41 in the Z-axis direction. The processing feed means 31 has a pair of guide rails 32 arranged in the column 14 and parallel to the Z-axis direction, and a motor-driven Z-axis table 33 slidably installed on the pair of guide rails 32. . A nut portion (not shown) is formed on the back side of the Z-axis table 33, and a ball screw 34 is screwed to the nut portion. The ball screw 34 is rotationally driven by a drive motor 35 connected to one end of the ball screw 34, whereby the polishing means 41 is processed and fed along the guide rail 32.

  The polishing means 41 is attached to the front surface of the Z-axis table 33 via the housing 42, and is configured by providing a polishing pad 46 below the spindle unit 43. The spindle unit 43 is provided with a flange 45, and the polishing means 41 is supported on the housing 42 via the flange 45. A platen 44 to which a suede type polishing pad 46 is attached is attached to the lower part of the spindle unit 43. The suede type polishing pad 46 is a flexible pad suitable for mirror polishing, and a large number of holes for fixing the slurry are formed on the polishing surface of the polishing pad 46.

  In addition, on the upper part of the spindle unit 43, slurry supply means 48 for supplying slurry between the upper surface 28 (see FIG. 4B) of the wafer W (chip C) and the polishing surface 61 (see FIG. 4B) of the polishing pad 46 is provided. It is connected. By supplying the slurry from the slurry supply means 48, the slurry is fixed on the polishing surface 61 through the flow path 47 (see FIG. 5) in the spindle unit 43. The slurry is an alkaline aqueous solution or an acidic aqueous solution containing abrasive grains, and contains, for example, abrasive grains of green carborundum, diamond, alumina, cerium oxide, and CBN (cubic boron nitride). The alkaline slurry is preferably used for polishing a silicon wafer, and the acidic slurry is preferably used for polishing an inorganic material wafer.

  The CMP polishing apparatus 1 is provided with a control unit (not shown) that controls each part of the apparatus. The control unit is configured by a processor, a memory, and the like that execute various processes. The memory is composed of one or a plurality of storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) depending on the application. In the CMP polishing apparatus 1 configured as described above, the polishing pad 46 approaches the holding table 21 while being rotated around the Z axis. Then, while the slurry is supplied, the polishing pad 46 is rotationally brought into contact with the chip C after the division of the wafer W, whereby the chip C is polished.

  By the way, in the present embodiment, unlike the polishing of the wafer W before division, the wafer W is divided into individual chips C by DBG (Dicing Before Grinding) or the like, so that polishing dust is likely to be generated during polishing. For example, as shown in FIG. 2, in the polishing using the polishing pad 96 in which the groove 92 is formed by cutting, the slurry is easily fixed to the polishing pad 96 through the groove 92. There is a problem that the polishing pad 96 is easily cut off on the upper side. That is, in the groove 92 formed by cutting on the polishing pad 96, a corner 94 is formed between the groove side surface 93 and the polishing surface 91, and the corner 94 of the polishing pad 96 repeatedly hits the corner 29 or the upper side of the chip C. This makes it easier to cut out.

  The present inventors pay attention to the fact that the groove 62 (see FIG. 3) of the polishing pad 46 is notched into the chip C from the corner side, so that the groove 62 of the polishing pad 46 that is likely to be notched into the chip C is chamfered. I have to. Further, the polishing pad 46 is formed of a thermoplastic resin, and the groove 62 and the chamfer 65 are formed by thermoplastic deformation, so that the chip C is hardly caught on the chamfer 65 or the groove side surface 63. Thereby, the notch of the polishing pad 46 by the chip C is suppressed, the flatness of the polishing surface 61 is maintained, and the adhesion of polishing dust to the chip C is suppressed.

  Hereinafter, the polishing pad will be described in detail with reference to FIG. FIG. 3A is a perspective view of the polishing pad according to the present embodiment. FIG. 3B is a cross-sectional view of the polishing pad according to the present embodiment. FIG. 4 is an explanatory diagram of the polishing process using the polishing pad according to the present embodiment. In addition, the thick line shown to FIG. 3B and FIG. 4 has shown the state which the hole of the polishing pad was crushed. 4A and 4B show a polishing process using the polishing pad according to the present embodiment, and FIG. 4C shows a polishing process using the polishing pad according to the comparative example.

  As shown in FIGS. 3A and 3B, the polishing pad 46 is a suede pad attached to the platen 44, and is formed in a circular plate shape with a flexible thermoplastic resin. The polishing surface 61 of the polishing pad 46 is provided with a plurality of intersecting grooves 62 that serve as passages for the slurry. The groove 62 has a groove side surface 63 that faces the polishing surface 61 at a predetermined depth, and a groove bottom surface 64 that is connected to the groove side surface 63 that faces the groove. A chamfer 65 is provided at a connection portion between the polishing surface 61 and the groove side surface 63, and the corner of the groove 62 is rounded by the chamfer 65 so that the polishing surface 61 and the groove side surface 63 are gently connected.

  The groove 62 and the chamfer 65 are formed by partially subjecting the polishing surface 61 to thermoplastic deformation, and a large number of holes on the surfaces of the chamfer 65 and the groove 62 are crushed. As a result, the surfaces of the chamfer 65 and the groove side surface 63 are relatively smooth and are not easily caught by the corners of the chip C. In other words, the surface of the polishing pad 46 excluding the groove 62 and the chamfer 65 functions as a polishing surface 61 in which a large number of holes are left. A slurry supply hole 68 connected to the slurry supply means 48 (see FIG. 1) is formed at the center of the polishing surface 61.

  In the polishing process using the polishing pad 46, the slurry supplied from the slurry supply hole 68 receives the centrifugal force generated by the rotation of the polishing pad 46 and is spread outside the polishing pad 46. The slurry passes toward the outside of the polishing pad 46 through the groove 62, and is supplied from the inside of the groove 62 to the many holes of the polishing surface 61 through the surface of the chamfer 65. As described above, since the chamfer 65 is formed in the groove 62 of the polishing pad 46, the slurry in the groove 62 easily spreads over the entire polishing surface 61. The slurry enters and is fixed in a number of holes in the polishing surface 61, and the surface of the chip C (see FIG. 4B) is polished by the polishing surface 61.

  As shown in FIG. 4A, the polishing pad 46 according to the present embodiment has grooves 62 and chamfers 65 formed so as to crush the polishing surface 61 by thermoplastic deformation by hot pressing. The groove 62 and the chamfer 65 are in a state in which a large number of holes are crushed, and the surface is hardened and is smoothly formed. In this case, the surface of the chamfer 65 is entirely crushed from the groove side surface 63 to the polishing surface 61, and the chip C is hardly caught by the entire chamfer 65. On the other hand, the polished surface 61 is a portion that is not thermoplastically deformed and has a soft surface and a large number of holes. A method for forming the groove 62 and the chamfer 65 will be described later.

  As shown in FIG. 4B, in the polishing process using the polishing pad 46, the polishing pad 46 is pressed against the chip C and deformed. Due to the deformation of the polishing pad 46, a part of the chamfer 65 is pushed out toward the polishing surface 61, and not only the polishing surface 61 but also a part of the chamfer 65 comes into contact with the surface 28 of the chip C. As a result, a portion where the chip C is not easily caught as shown by a thick line exists up to the boundary of the polishing surface 61, and even if the corner 29 of the chip C hits the vicinity of the boundary of the polishing surface 61, it is difficult to be cut out. In this case, since the groove side surface 63 and the polishing surface 61 are connected by the chamfer 65 with a curved surface, the contact of the chip C with the chamfer 65 is softened, and the chamfer 65 is guided to the polishing surface 61 without being cut out.

  On the other hand, as shown in FIG. 4C, the chamfer 85 of the polishing pad 86 according to the comparative example is formed in a state in which only the hole in the vicinity of the groove side surface 83 is crushed by the thermoplastic deformation by hot pressing. For this reason, when the polishing pad 86 is pressed against the chip C, a part of the chamfer 85 is pushed out toward the polishing surface 81 due to the deformation of the polishing pad 86, but a hole in a part of the surface of the pushed chamfer 85 is crushed. Absent. That is, there is no portion in the vicinity of the polishing surface 81 where the chip C as shown by the thick line is difficult to be caught. For this reason, when the corner 29 of the chip C hits the vicinity of the boundary of the polishing surface 81, the polishing surface 81 is notched by the corner 29 of the chip C, and polishing dust D is generated.

  As described above, in the polishing pad 46 according to the present embodiment, not only the groove 62 and the chamfer 65 are formed by hot pressing, but when the polishing pad 46 is pressed against the chip C, the hole of the chamfer 65 is crushed. A groove 62 is formed so that the spot is positioned in the same plane as the polishing surface 61. This effectively protects a portion of the polishing surface 61 that is easily scraped by the corner 29 of the chip C, maintains the flatness of the polishing surface 61, and suppresses adhesion of the polishing dust D to the chip C.

  The CMP polishing method will be described with reference to FIG. FIG. 5 is an explanatory diagram of the CMP polishing method according to the present embodiment. 5A shows the holding process, and FIG. 5B shows the CMP polishing process.

  As shown in FIG. 5A, a holding step is first performed. In the holding step, the wafer W divided by DBG or the like is carried into the holding table 21 in a state of being attached to the protective tape T. The divided wafer W is held by the holding table 21 via the protective tape T when the protective tape T is sucked by the holding table 21. Further, the holding table 21 is moved below the polishing means 41 and the polishing surface 61 of the polishing pad 46 is opposed to the wafer W. Further, since the wafer W is divided into a plurality of chips C, each chip C has a corner 29 that hits the polishing surface 61.

  As shown in FIG. 5B, a CMP polishing step is performed after the holding step. In the CMP polishing process, the holding table 21 is rotated about the Z axis, and the polishing pad 46 is also rotated about the Z axis. Then, the polishing pad 46 is processed and fed toward the wafer W, and the polishing surface 61 of the polishing pad 46 is brought close to the divided wafer W. The polishing surface 61 of the polishing pad 46 is brought into rotational contact with the wafer W, and the divided wafer W is polished using the polishing pad 46 while the slurry is supplied. The slurry spreads over the entire polishing surface 61 through the intersecting grooves 62 of the polishing pad 46 and is fixed to a number of holes in the polishing surface 61.

  Further, as described above, the surface of the groove 62 and the chamfer 65 of the polishing pad 46 has many holes crushed so that it is difficult to be caught on the corner 29 of the chip C. Therefore, even if the corner 29 of the chip C repeatedly hits the surface of the groove 62 of the polishing pad 46, the polishing surface 61 is hardly cut out. Therefore, it is possible to polish the divided wafer W by fixing the slurry on the polishing surface 61 and to reduce the polishing dust D (see FIG. 4C) by suppressing the notch of the polishing surface 61 by the corner 29 of the chip C. It has become. Therefore, it is possible to continue polishing the wafer W satisfactorily while maintaining the flatness of the polishing pad 46, and the adhesion of the polishing dust D to the chip C is suppressed.

  With reference to FIG. 6, the manufacturing method of a polishing pad is demonstrated. FIG. 6 is an explanatory diagram of a method for manufacturing a polishing pad according to the present embodiment. Note that the manufacturing method of the polishing pad in FIG. 6 is merely an example, and the present invention is not limited to this manufacturing method.

  As shown in FIG. 6, the polishing pad 46 is manufactured by hot pressing a suede cloth 74 by a hot press device 70. The hot press device 70 is configured to press a press upper platen 72 to which a press die 73 is attached against a suede base cloth 74 placed on the press lower platen 71. A flat placing surface 71 a on which the suede base cloth 74 is placed is formed on the upper surface of the lower press platen 71. A frame body 75 for positioning the suede base cloth 74 placed on the press lower surface plate 71 is provided on the outer peripheral side of the lower surface of the press upper surface plate 72, and a groove 62 and a suede base cloth 74 are formed inside the frame body 75. A grid-like press die 73 for forming the chamfer 65 is provided.

  The press die 73 is heated by a heater (not shown) provided on the press upper platen 72. The press mold 73 has a thickness that prevents the upper press platen 72 from contacting the suede cloth 74 during hot pressing. At the time of hot pressing, even if the suede base cloth 74 is partially pushed by the press mold 73, the press upper surface plate 72 is separated from the surface of the suede base cloth 74, and is not pushed by the press mold 73. Is not affected by heat. Therefore, only a predetermined portion of the suede base cloth 74 pushed in by the press die 73 is thermoplastically deformed and the surface state changes.

  In such a heat press apparatus 70, the suede base cloth 74 is placed on the press lower surface plate 71, and the press upper surface plate 72 is put on the suede base cloth 74 from above so that the suede base cloth 74 fits in the frame body 75. . Then, the suede base cloth 74 is pushed in by the heated press mold 73, and the suede base cloth 74 is thermoplastically deformed along the grid-like press mold 73. Thereby, the groove | channel 62 and the chamfer 65 are formed in the surface of the suede raw fabric 74, and the polishing pad 46 is manufactured.

  As described above, in the polishing pad 46 according to the present embodiment, since the grooves 62 intersecting the polishing surface 61 are formed, the slurry spreads over the entire polishing surface 61 through the grooves 62, and the divided wafer W is excellent. Can be polished. Further, a corner 94 is not formed between the polishing surface 61 and the groove side surface 63 of the polishing pad 46 that is easily cut at the corner 29 of the chip C, and the chamfer 65 reduces the contact of the chip C with the corner 29. Further, since the chamfer 65 and the groove 62 are formed in the polishing pad 46 by thermoplastic deformation, the entire surface of the groove 62 and the chamfer 65 is crushed and the wafer W is hardly caught. Accordingly, the polishing surface 61 of the polishing pad 46 can be prevented from being cut out by the wafer W, the flatness of the polishing surface 61 can be maintained, and the polishing dust D of the polishing pad 46 can be reduced to suppress adhesion to the wafer W. Is possible.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in the above-described embodiment, the polishing pad 46 for polishing the divided wafer W has been described. However, the present invention is not limited to this configuration. Polishing pad 46 concerning this embodiment can also polish wafer W which is not divided.

  In the above-described embodiment, the suede type polishing pad 46 is used. However, the polishing pad 46 is not limited to the suede type. The polishing pad 46 may be a porous type or non-woven type polishing pad as long as the groove 62 and the chamfer 65 can be formed on the polishing surface 61 of the polishing pad 46 by thermoplastic deformation using a thermoplastic resin as a material.

  Further, in the above-described embodiment, the divided wafer W is attached to the protective tape T and carried into the CMP polishing apparatus 1, but is not limited to this configuration. The divided wafer W may be attached to a protective tape stretched on the ring frame and carried into the CMP polishing apparatus 1.

  In the above-described embodiment, the lattice-shaped grooves 62 are formed on the polishing surface 61 of the polishing pad 46. However, the present invention is not limited to this configuration. It suffices if the intersecting grooves 62 are formed on the polishing surface 61 of the polishing pad 46, and the grooves 62 may intersect obliquely.

  As described above, the present invention has an effect that the polishing surface of the polishing pad can be prevented from being cut out by the wafer during polishing, and in particular, the polishing pad and CMP polishing for polishing the wafer while supplying the slurry. Useful in the method.

21 Holding Table 46 Polishing Pad 61 Polishing Surface 62 Polishing Pad Groove 63 Polishing Pad Groove Side 64 Polishing Pad Groove Bottom 65 Polishing Pad Chamfer C Chip T Protection Tape W Wafer

Claims (2)

A polishing pad for polishing a wafer,
It is formed using a thermoplastic resin and has grooves that intersect the polished surface.
The groove has a groove side surface facing the polishing surface at a predetermined depth, and a groove bottom surface connected to the groove side surface facing the groove, and chamfers a connecting portion between the polishing surface and the groove side surface. Polishing pad provided. A protective tape is attached to one surface of a wafer having a division line, and the holding table holds the wafer divided along the division line, and supplies slurry to the wafer and the polishing pad. A CMP polishing method for polishing a wafer using the polishing pad according to claim 1,
A holding step of sucking the protective tape and holding the wafer divided through the protective tape with the holding table;
A CMP polishing method comprising, after the holding step, a CMP polishing step of supplying slurry and polishing the divided wafer using the polishing pad.

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