US20070190911A1

US20070190911A1 - Polishing pad and forming method

Info

Publication number: US20070190911A1
Application number: US11/725,679
Authority: US
Inventors: Shunichi Shibuki
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 2002-02-07
Filing date: 2007-03-20
Publication date: 2007-08-16
Also published as: KR20040079965A; US20050153633A1; TW200307588A; TWI266673B; CN1628374A; WO2003067641A1; CN100365773C; JP2003300149A; JP3843933B2

Abstract

A polishing pad which ensures that a work can be easily removed from the polishing pad surface after polishing, the amount of a polishing liquid used for polishing can be reduced, and the production cost of the polishing pad can be lowered. A first polishing pad (1) for polishing a work is provided with a plurality of slots (11) piercing the first polishing pad (1) in a sa direction, the length in the longitudinal direction of the slots (11) being preferably not less than 20 mm, the pitch in the width direction of the slots (11) being preferably less than 100 mm, and small holes (not shown) may be provided in addition to the slots (11).

Description

TECHNICAL FIELD

The present invention relates to a polishing pad, a polishing apparatus and a polishing method, and particularly to a polishing pad provided with a plurality of slots, a polishing apparatus using the polishing pad, and a polishing method using the polishing pad.

BACKGROUND ART

As Related Art 1, there have been commercialized polishing pads which are provided grooves in the surface thereof. For example, there is available the polishing pad IC1000-A22 produced by Rodel Nitta Company. As shown in FIG. 9, this polishing pad 61 is provided in its polishing pad surface 61S with grooves 62, 2 mm in width, in a lattice pattern at a pitch of about 2 cm. Incidentally, the grooves 62 are omitted in the plan view.
As Related Art 2, there have been commercialized polishing pads provided with a plurality of small holes (for example, small holes of 1.8 mm in diameter) in the surface thereof. One example known of this type of polishing pads is the polishing pad IC1000(p) produced by Rodel Nitta Company.
As Related Art 3, there has been disclosed, as shown in FIG. 10, a polishing pad 71 which is provided with a plurality of holes 72 and with a plurality of grooves 73 in its surface 71S. Incidentally, the holes 72 and the grooves 73 are omitted in the plan view. No description is given about the diameter of the holes in Japanese Patent No. 3042593. Generally, however, the polishing pads provided with holes of 1.8 mm in diameter in a density of about 3 to 5 pieces/cm²are often used. Incidentally, it is described in Japanese Patent No. 3042593 that the width of the grooves may be not more than the diameter of the holes, that the depth of the grooves may be about 0.3 mm, and that the groove depth may be up to 0.5 mm (see, for example, Patent Document 1).
In the polishing pad according to Related Art 3, provision of the holes restrains the polishing resistance from increasing. In addition, with the grooves formed in the polishing pad surface, the hermetic seal property between the polishing pad surface and a semiconductor wafer is lowered, so that a negative pressure is less liable to be generated there. Therefore, it is easy to remove the semiconductor wafer from the polishing pad surface after completion of the polishing. Besides, the polishing pad according to Related Art 3 has the characteristic features that the strength of the hard layer is restrained from being lowered, the load on the soft layer is reduced, and deterioration thereof with time is suppressed, as compared to the polishing pads provided with ordinary grooves.
In addition, chemical mechanical polishing (hereinafter referred to as CMP) has been used, for example, at the time of planarizing the surface of an insulation film in the manufacturing process of a semiconductor device, and at the time of removing surplus materials in the formation of copper wirings, tungsten plugs or the like.
A CMP apparatus which has been widely used has a structure in which the polishing surface of the polishing pad is planar, the surface to be polished of a wafer and the polishing surface of the polishing pad are disposed parallel to each other, and they make contact while being rotated respectively, whereby polishing is performed (see, for example, Patent Document 2).
Furthermore, there have been known a belt-type CMP apparatus (see, for example, Patent Document 3), (see, for example Patent Document 4), a rectilinear oscillation type CMP apparatus (see, for example, Patent Document 5), a CMP apparatus comprising a ring-shaped polishing pad (see, for example, Patent Document 6), and a roller-type CMP apparatus (see, for example, Patent Document 7). In every one of the above-mentioned polishing apparatuses, the polishing surface of the polishing pad brought into contact with the surface to be polished is planar.
Patent Document 1: Japanese Patent Laid-open No. Hei 9-117855 (p. 4, FIG. 1, FIG. 5)
Patent Document 2: Japanese Patent Laid-open No. 2000-218514 (p. 4, FIG. 5)
Patent Document 3: Japanese Patent Laid-open No. 2000-218514 (p. 4, FIG. 6)
Patent Document 4: Japanese Patent Laid-open No. Hei 8-52652 (pp. 5-6, FIG. 1)
Patent Document 5: Japanese Patent Laid-open No. Hei 8-52652 (p. 8, FIG. 10)
Patent Document 6: Japanese Patent Laid-open No. Hei 11-31671 (p. 5, FIG. 1)
Patent Document 7: Japanese Patent Laid-open No. Hei 2-139172 (pp. 3-5, FIGS. 1 to 3)
However, the polishing pad according to the above-mentioned Related Art 1 has the problem that the polishing liquid would flow out through the grooves during polishing, and a large amount of the polishing liquid is needed. Besides, since the grooves are formed by cutting, the production cost of the polishing pad is higher, as compared with polishing pads which are provided with holes by punching.
The polishing pad according to the Related Art 2 has the disadvantage that the polishing resistance is raised because a negative pressure is generated between the polishing pad and the work in the areas of the holes. Furthermore, it is difficult to remove the work from the polishing pad after completion of the polishing. A detailed description of this phenomenon is given also in Japanese Patent Laid-open No. Hei 9-117855.
The polishing pad according to the Related Art 3 has the drawback that the production cost thereof is high, since the grooves must be formed by cutting after the formation of the holes by punching.
The problems involved in the polishing pads as above-mentioned cannot be solved by the polishing apparatuses and polishing methods using the polishing pads described in the above-mentioned Related Arts.

DISCLOSURE OF INVENTION

The present invention pertains to a polishing pad, a polishing apparatus, and a polishing method invented for solving the above-mentioned problems.
The first polishing pad according to the present invention is a polishing pad for polishing a work, which is provided with a plurality of slots piercing through the polishing pad in the thickness direction.
In the first polishing pad, since the plurality of slots piercing through the polishing pad in the thickness direction are provided, the hermetic seal property between the surface to be polished and the polishing pad surface is lowered, so that a negative pressure is less liable to be generated there. Accordingly, it is easy to remove the work from the polishing pad surface after completion of polishing. In addition, since the slots formed in the polishing pad according to the present invention can be formed by punching, the polishing pad is lower in production cost than a polishing pad provided with grooves formed by cutting.
The second polishing pad according to the present invention is a polishing pad for polishing a work, which is provided with a plurality of holes piercing through the polishing pad in the thickness direction, part of the plurality of holes being composed of slots.
In the second polishing pad, since the plurality of holes piercing through the polishing pad in the thickness direction are provided and part of the plurality of holes are composed of clots, the hermetic seal property of between the surface to be polished and the polishing pad surface is lowered due to the presence of the slots and a negative pressure is less liable to be generated there, in the same manner as in the case of the first polishing pad. Therefore, it is easy to remove the work from the polishing pad surface after completion of polishing. Further, since a plurality of holes other than the slots are provided, the polishing resistance is restrained from increasing. Furthermore, since grooves are not provided in the present polishing pad, unlike the related-art polishing pads, there is no possibility that a polishing liquid might flow out through grooves to the exterior of the polishing pad. The slots formed in the polishing pad according to the present invention reserve the polishing liquid therein, which makes it possible to reduce the amount of the polishing liquid used. In addition, since the plurality of holes inclusive of the slots which are formed in the polishing pad according to the present invention can be formed by a single punching operation, the polishing pad is lower in production cost than the polishing pads provided with grooves which are formed by cutting. Further, since the slots are so formed as to pierce through the polishing pad in the thickness direction, the slots are not lost even when the polishing pad is worn as polishing proceeds. Accordingly, the polishing pad according to the present invention can show a longer pad life, as compared with the polishing pads provided with grooves.
A polishing apparatus according to the present invention is a polishing apparatus which uses a polishing pad according to the present invention, whereby the production cost of the polishing pad can be lowered. Since a polishing pad according to the present invention is thus used, the operating cost of the polishing apparatus is lowered. Furthermore, since the polishing pad according to the present invention has a longer pad life than that of a related-art polishing pad provided with grooves, the frequency of replacement of the polishing pad is reduced.
A polishing method according to the present invention is a polishing method in which a polishing pad according to the present invention is used, whereby the production cost of the polishing pad can be lowered. Since a polishing pad according to the present invention is thus used, polishing cost is lowered. Furthermore, since the polishing pad according to the present invention has a longer pad life than that of a related-art polishing pad provided with grooves, the frequency of replacement of the polishing pad is reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a plan view and a partly enlarged view illustrating a first embodiment of the first polishing pad according to the present invention.
FIG. 2 shows a plan view and a partly enlarged view illustrating a first embodiment of the second polishing pad according to the present invention.
FIG. 3 is a plan view showing an embodiment of slots formed in the first and second polishing pads according to the present invention.
FIG. 4 is a plan view showing another embodiment of slots formed in the first and second polishing pads according to the present invention.
FIG. 5 is a plan view illustrating a second embodiment of the first polishing pad according to the present invention.
FIG. 6 shows a plan view illustrating a second embodiment of the second polishing pad according to the present invention.
FIG. 7 is a schematic configurational perspective view illustrating an embodiment of the first polishing apparatus according to the present invention.
FIG. 8 is a schematic configurational perspective view illustrating an embodiment of the second polishing apparatus according to the present invention.
FIG. 9 shows a plan view, a partly enlarged view and a sectional view along line A-A′ illustrating a polishing pad according to Related Art 1.
FIG. 10 shows a plan view, a partly enlarged view and a sectional view along line B-B′ illustrating a polishing pad according to Related Art 3.

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of the first polishing pad according to the present invention will be described referring the plan view and the partly enlarged view shown in FIG. 1.
As shown in FIG. 1, the first polishing pad 1 is provided with a plurality of slots 11 piercing through the polishing pad 1 in the thickness direction, the slots 11 being aligned in the row direction and the column direction. The polishing pad 1 is formed of a resin, for example, foamed polyurethane or urethane. Its thickness is comparable to those of ordinary polishing pads, and is, for example, about 0.5 to 3.0 mm. The slots 11 are so formed as to be included in the polishing pad 1, and their length L in the longitudinal direction is not less than 20 mm. In addition, the slots 11 are formed at a pitch p which is not less than twice the length in the transverse direction (hereinafter referred to as the width) W thereof and is less than 100 mm. Incidentally, the spacing d in the longitudinal direction of the slots 11 is appropriately set; here, as an example, the spacing d is 10 mm. Besides, the slots 11 may be formed to be staggered from each other in either one or both of the row direction and the column direction.
Since the first polishing pad is provided with the plurality of slots 11 piercing through the first polishing pad 1 in the thickness direction, the hermetic seal property between the surface to be polished and the surface of the polishing pad 1 is lowered and a negative pressure is less liable to be generated there, so that it is easy to remove the work from the surface of the polishing pad 1 after completion of polishing. In addition, the slots 11 formed in the first polishing pad 1 according to the present invention can be formed by punching, the polishing pad 1 is lower in production cost than a polishing pad provided with grooves by cutting. Further, since the slots 11 are so formed as to piece through the first polishing pad 1 in the thickness direction, the slots 11 are not lost even when the first polishing pad 1 is worn. Therefore, the first polishing pad 1 can show a prolonged pad life, as compared with the related-art polishing pads provided with grooves.
Next, a first embodiment of the second polishing pad according to the present invention will be described referring to the plan view and the partly enlarged view shown in FIG. 2. Incidentally, small holes are omitted in the plan view.
As shown in FIG. 2, the second polishing pad 2, like the first polishing pad 1, is provided with slots 11 piercing through the second polishing pad 2 in the thickness direction in the state of being aligned, for example, in the row direction and the column direction, and is provided with a plurality of holes (hereinafter referred to as small holes) 21 piercing through the second polishing pad 2 in the thickness direction and having a diameter D of 10 mm or below, preferably, 5 mm or below. Specifically, the slots 11 are included in the polishing pad 1, and have a length L of not less than 20 mm. In addition, the slots 11 are formed at a pitch p1 of not less than twice the width W thereof and less than 100 mm. Incidentally, the spacing d in the longitudinal direction of the slots 11 is appropriately set; here, as an example, the pitch p1 is 10 mm. In addition, the slots 11 may be formed to be staggered from each other in either one or both of the row direction and the column direction.
Further, the small holes 21 are composed of holes having a diameter D=1.8 mm, for example, and are uniformly arranged in a lattice point pattern at pitches p2 x=p2 y=5 mm. Incidentally, the small holes 21 are preferably so formed as not to overlap with the slots 11. Besides, the arrangement of the small holes 21 is not limited to the lattice point pattern, inasmuch as the small holes 21 are formed at predetermined pitches over the entire surface area of the polishing pad.
In the second polishing pad 2, since there are provided the pluralities of slots 11 and small holes 21 piercing through the second polishing pad 2 in the thickness direction, the hermetic seal property between the surface to be polished and the surface of the second polishing pad 2 is lowered due to the presence of the slots 11, so that a negative pressure is less liable to be generated there, like in the case of the first polishing pad 1. Therefore, it is easy to remove the work from the surface of the second polishing pad 2 after completion of polishing. In addition, since the slots 11 reserve the polishing liquid therein, it is possible to reduce the amount of the polishing liquid used.
Further, since the plurality of small holes 21 other than the slots 11 are provided, the polishing resistance can be prevented from increasing. Furthermore, since grooves are not provided, unlike the related-art polishing pads, there is no possibility that the polishing liquid might flow out through grooves to the exterior of the polishing pad.
In addition, since the slots 11 and the small holes 21 formed in the second polishing pad 2 according to the present invention can be formed by a single punching operation, the production cost is lower than that of a polishing pad provided with grooves by cutting.
Further, since the slots 11 and the small holes 21 are so formed as to pierce through the second polishing pad 2 in the thickness direction, the slots 11 and the small holes 21 are not lost even when the second polishing pad 2 is worn as polishing proceeds. As a result, the second polishing pad 2 can show a prolonged pad life, as compared with polishing pads provided with grooves.

Next, the possibility of generation of troubles during conveying of polishing pads was investigated by using the first and second polishing pads 1 and 2 and varying the length of the slots, the width of the slots, and the pitch in the width direction of the slots. The spacing d in the longitudinal direction of the slots 11 shown in FIGS. 1 and 2 was fixed at 10 mm. In each polishing, a silicon wafer provided on its surface with a solid film of silicon oxide was used as a work, the silicon oxide film as a surface to be polished was polished once, and it was checked 10 times if the silicon wafer could conveyed. The results are summarized in Table 1 below.

TABLE 1


							IC1000/SUBA400	IC1000/SUBA400
					IC1000/SUBA400	IC1000/SUBA400	laminate	laminate
			IC1000	IC1000	laminate	laminate	Without	With small holes
			monolayer	monolayer	Without	With small holes	small holes	Both slots and
Length	Width of	Pitch of	Without	With	small holes	Both slots and	Slots piercing	small holes
of slots	slots	slots	small	small	Slots in IC1000	small holes in	through	piercing through
(mm)	(mm)	(mm)	holes	holes	only	IC1000 only	IC1000/SUBA400	IC1000/SUBA400

10	2	40	0.3	0.8	0.4	1	0.4	1
20	0.5	10	0	0	0	0	0	0
	1	20	0	0	0	0	0	0
	2	100	0	0.2	0	0.3	0	0.4
		40	0	0	0	0	0	0
		25	0	0	0	0	0	0
		20	0	0	0	0	0	0
		10	0	0	0	0	0	0
30	2	40	0	0	0	0	0	0
40	2		0	0	0	0	0	0
50	2		0	0	0	0	0	0

Without slots	0.2	0.7	0.2	1	0.1	1

In the above investigation, a foamed polyurethane-made polishing pad (for example, the IC1000 monolayer product, 1.2 mm thick, produced by Rodel Inc.) and a laminated polishing pad comprising a foamed polyurethane-made upper layer and a PET (polyethylene terephthalate)-made lower layer (for example, a laminated polishing pad comprising a 1.2 mm-thick upper layer formed of IC1000 produced by Rodel Inc. and a 1.2 mm-thick lower layer formed of SUBA400 produced by Rodel Inc.) were used as the first and second polishing pads 1 and 2.
The first and second polishing pads 1 and 2 were each adhered to a polishing surface plate (not shown) by use of a double-faced pressure sensitive adhesive tape in the case where the polishing pad was a monolayer product. In the above investigation, in order that a slurry does not make direct contact with the polishing surface plate, the first and second polishing pads 1 and 2 were provided with slots 11, small holes 21 or the like by punching, and then were each adhered to the polishing surface plate by use of a double-faced pressure sensitive adhesive tape. Incidentally, when the double-faced pressure sensitive adhesive tape is adhered to the first and second polishing pads 1 and 2 and then they are provided with the slots 11, the small holes 21 or the like by punching, combinations of the polishing pad and the pressure sensitive adhesive tape with the holes formed also in the pressure sensitive adhesive tape are obtained. Even where the double-faced pressure sensitive adhesive tape is thus also provided with the slots 11 and/or the small holes 21, the effects of the present invention are not thereby influenced at all.
On the other hand, the laminated products (laminates) prepared included those provided with holes piercing through IC1000 only and those with holes piercing through both IC1000 and SUBA400. Since IC1000 and SUBA400 are adhered by use of the double-faced pressure sensitive adhesive tape, the laminated product with holes piercing through IC1000 only can be obtained when IC1000 is provided with the holes by punching before adhesion, whereas the laminate product with holes piercing through both IC1000 and SUBA400 can be easily obtained when formation of the holes by punching is conducted after adhesion.
IC1000 was adhered to SUBA400 by use of a double-faced pressure sensitive adhesive tape. In this case, of the laminate products with holes piercing through IC1000 only, those with the double-faced pressure sensitive adhesive tape being not provided with holes can be obtained when punching is conducted before adhesion of the double-faced pressure sensitive adhesive tape to IC1000, whereas those with the double-faced pressure sensitive adhesive tape being provided with holes can be obtained when punching is conducted after adhesion of the double-faced pressure sensitive adhesive tape. The effects of the present invention are not affected by whether or not the double-faced pressure sensitive adhesive is provided with holes. In the investigation, the laminated products with the double-faced pressure sensitive adhesive tape being free of holes were prepared and used, in view of that such laminated products are free of penetration of the slurry to the lower layer formed of SUBA400.
The laminated products with holes piercing through both IC1000 and SUBA400 were each adhered to the polishing surface plate by use of a double-faced pressure sensitive adhesive tape. Of the laminated products, those with the double-faced pressure sensitive adhesive tape being not provided with holes can be obtained when punching is conducted before adhesion of the double-faced pressure sensitive adhesive tape, whereas those with the double-faced pressure sensitive adhesive tape being provided with holes can be obtained when punching is conducted after adhesion of the double-faced pressure sensitive adhesive tape. The effects of the present invention are not influenced by whether or not the double-faced pressure sensitive adhesive tape is provided with holes. In the investigation, the laminated products with the double-faced pressure sensitive adhesive tape being free of holes were prepared and used, in view of that such laminated products are free of direct contact of the slurry with the polishing surface plate.
From Table 1 it is seen that, in the case where the first polishing pad 1 composed of an IC1000 monolayer had been provided with slots 11 having a length of not less than 20 mm, no error was generated in conveying the wafer. However, it should be noted here that, in the case of the second polishing pad 2 provided with both small holes 21 as well as slots 11, a conveying error was generated when the pitch p of the slots 11 reached or exceeded 100 mm.
In addition, in the case of the first polishing pad 1 composed of an IC1000-SUBA400 laminate and provided with slots 11 piercing through only IC1000, no error was generated in conveying the wafer when the length of the slots 11 was not less than 20 mm. In the case of the second polishing pad 2 provided with small holes 21 as well as slots 11, however, a conveying error was generated when the pitch p of the slots 11 reached or exceeded 100 mm.
In addition, in the case of the first polishing pad 1 composed of an IC1000-SUBA400 laminate and provided with slots 11 piercing through both IC1000 and SUBA400, no error was generated in conveying the wafer when the length of the slots 11 was not less than 20 mm. In the case of the second polishing pad 2 provided with small holes 21 as well as slots 11, however, a conveying error was generated when the pitch p of the slots 11 reached or exceeded 100 mm.
Besides, in the lowermost row of Table 1, the results obtained with the polishing pads not provided with slots 11 are shown as a comparative example. As a result, a wafer conveying error was generated, irrespectively of whether the polishing pad was a monolayer product or a laminate and whether or not the polishing pad was provided with small holes. This shows that the presence of the slots 11 is effective for preventing the wafer conveying errors from being generated.
Accordingly, it has been found out that the length of the slots 11 should be not less than 20 mm. Further, it was also found that the pitch p in the width direction of the slots should be less than 100 mm. Besides, the lower limit of the width of the slots 11 was set to be twice the width of the slots 11, taking into account the rigidity of the polishing pad in the areas between the slots 11.
Next, an embodiment of slots formed in the first and second polishing pads according to the present invention will be described referring to the plan view shown in FIG. 3.
As shown in FIG. 3, the first polishing pad 1 (the second polishing pad 2) may be provided with slots 11 which are arranged radially. While the polishing pad provided with one slot 11 in a radial direction is shown in the figure, the polishing pad may be provided with a plurality of slots in a radial direction. Besides, while small holes 21 are omitted in FIG. 3, the polishing pad may be provided with small holes 21, as has been described referring to FIG. 2. Incidentally, the arrangement of the small holes 21 is not limited to the lattice point pattern, inasmuch as the small holes 21 are formed at predetermined pitches over the entire surface area of the polishing pad.
In the polishing pad configured as above-described, by providing the slots 11 with a sufficient length, for example, a length greater than the radius of the work (e.g., wafer) and arranging the slots 11 radially, it is possible to obtain a structure which ensures that a negative pressure is less liable to be generated on the wafer. With such slots 11 formed by punching, the slots 11 can be formed in a comparatively freer shape, as compared with grooves. This is one of the advantages of the present configuration.
Next, another embodiment of the slots formed in the first and second polishing pads according to the present invention will be described referring to the plan view shown in FIG. 4.
As shown in FIG. 4, the first polishing pad 1 (the second polishing pad 2) may be provided with circular arc-shaped slots 11 which are arranged concentrically, for example. While the case where two rows of the slots 11 are formed concentrically is shown in the figure, the slots 11 may be formed in three or more rows. Besides, while small holes 21 are omitted in FIG. 4, the polishing pad may be provided with small holes 21, as has been described referring to FIG. 2. Incidentally, the arrangement of the small holes 21 is not limited to the lattice point pattern, inasmuch as the small holes 21 are formed at predetermined pitches over the entire surface area of the polishing pad.
In the polishing pad configured as above, by setting the length of the slots 11 to be, for example, sufficiently greater than the radius of the work (e.g., wafer) and forming the slots 11 in an arcuate shape, it is possible to obtain a structure which ensures that a negative pressure is less liable to be generated on the wafer and that the slurry holding property is enhanced, as compared with the cases of a parallel or radial arrangement, whereby the amount of the slurry used can be reduced. With the slots 11 and the small holes 21 thus formed by punching, they can be formed in comparatively freer shape, as compared with grooves. This is one of the advantages of the present configuration.
Next, a second embodiment of the first polishing pad according to the present invention will be described referring to the plan view shown in FIG. 5. In FIG. 5, there is shown a rectangular polishing pad, as used on a belt-type polishing apparatus. Incidentally, small holes are omitted in the plan view.
As shown in FIG. 5, the polishing pad 5 is provided with a plurality of slots 11 piercing through the polishing pad 5 in the thickness direction, the slots 11 being aligned in the row direction and the column direction. The polishing pad 5 is formed, for example, of a resin such as foamed urethane and urethane. The thickness of the polishing pad 5 is comparable to those of ordinary polishing pads, and is about 0.5 to 3.0 mm, for example. The slots 11 are included in the polishing pad 5, and the length L in the longitudinal direction thereof is not less than 20 mm. Besides, the slots 11 are formed at a pitch p which is not less than twice the length W in the transverse direction thereof (hereinafter referred to as width) and is less than 100 mm. Incidentally, the spacing d in the longitudinal direction of the slots 11 is appropriately set; here, the spacing d is set to be 10 mm, as an example. In addition, the slots 11 may be formed to be staggered from each other in either one or both of the row direction and the column direction.
Next, a second embodiment of the second polishing pad according to the present invention will be described referring to the plan view and the partly enlarged view shown in FIG. 6. Incidentally, small holes are omitted in the plan view. The symbols to be used in the following description are the same as those used in FIGS. 2 and 5.
As shown in FIG. 6, the polishing pad 6 according to this second embodiment is the polishing pad 5 as described referring to FIG. 5 which is provided with the same small holes 21 as described referring to FIG. 2. Namely, the polishing pad 6 is provided with slots 11 piercing through the polishing pad 6 in the thickness direction in the state of being aligned, for example, in the row direction and the column direction, and is provided also with a plurality of small holes 21 piercing through the polishing pad 6 in the thickness direction and having a diameter D of not more than 10 mm, preferably not more than 5 mm. Specifically, the slots 11 are included in the polishing pad 6, have a length L of not less than 20 mm, and are formed at a pitch p1 which is not less than twice the width W thereof and is less than 100 mm. Incidentally, the spacing d in the longitudinal direction of the slots 11 is appropriately set; here, the spacing d is set to 10 mm, as an example. Besides, the slots 11 may be formed to be staggered from each other in either one or both of the row direction and the column direction.
Furthermore, the small holes 21 are composed of holes having a diameter D=1.8 mm, for example, and are uniformly arranged in a lattice point pattern with pitches p2 x=p2 y=5 mm. Incidentally, it is preferable that the small holes 21 are so formed as not to overlap with the slots 11. In addition, the arrangement of the small holes 21 is not limited to the lattice point pattern, inasmuch as the small holes 21 are formed at predetermined pitches over the entire surface area of the polishing pad.
While the slots 11 are formed in parallel to the driving direction of the belt in the above configuration, the direction in which the slots 11 are arranged may be slant relative to the belt driving direction or perpendicular to the belt driving direction.
While the case where the slots 11 and the small holes 21 are formed by a single punching operation has been described in the above-described embodiments, the slots 11 and the small holes 21 may be formed by punching independently from each other. Such a method promises easier production of the polishing pad in the cases where it is desired, for example, to enlarge the width of the slots 11 as compared with the pitch of the small holes 21. Specific examples of such cases include a case where it is desired to form the small holes 21 at a pitch of 5 mm and to form slots 11 having a width of 7 mm. Another example is a case where the slots 11 and the small holes 21 overlap with each other in an area or areas. Specific example of this is a case where the small holes 21 are arranged in a lattice point pattern and the slots 11 are arranged radially or in a circular arc-shaped pattern.
In addition, where the polishing pad is provided with a window for optical detection of an end point, it is preferable to form no hole in the window portion, for ensuring that the light incident on the wafer is not intercepted. However, provision of the window with holes would not change the effectiveness of the present invention.
While IC1000 has been used as an example of the polishing pad in the above-described embodiments, the same effects as above-mentioned can be obtained irrespectively of the material of the polishing pad, namely, by using a nonwoven fabric-made polishing pad, sueded polishing pad, or other resin-made polishing pad or the like which is commercially available. In addition, even where a polishing pad comprising fixed abrasive grains is used, the effectiveness of the present invention remains unchanged, and the same effects as above-mentioned can be obtained.
Next, the polishing apparatuses according to the present invention will be described referring to the schematic configurational perspective views shown in FIGS. 7 and 8.
The first polishing apparatus is a polishing apparatus for polishing a surface to be polished of a material to be polished, by bringing a polishing pad into contact with the surface and into a frictional motion relative to the surface, wherein the polishing apparatus comprises one of the above-described polishing pads 1 to 4.
Specifically, as shown in FIG. 7, the first polishing apparatus 101 comprises a polishing surface plate 111 which can be turned in the direction of arrow a, for example. The polishing surface plate 111 is turned through a rotary shaft 112 connected to a turning drive which is not shown. In addition, one of the polishing pads 1 to 4 described above referring to FIGS. 1 to 4 is mounted on the polishing surface plate 111. Here, the polishing pad 1 was mounted. Now, description will be made referring to the polishing pad 1. The polishing pad 1 is mounted by a general polishing pad mounting method, for example, a method using a pressure sensitive adhesive sheet (inclusive of pressure sensitive adhesive tape) or a pressure sensitive adhesive. Specifically, the above-described method is adopted.
A polishing head 115 is provided at a position opposed to the polishing surface plate 111 on which the polishing pad 1 is mounted, generally in opposition to a position deviated from the center of rotation of the polishing surface plate 111. The polishing head 115 can be freely raised and lowered. Further, the polishing pad 115 is turned, for example, in the direction of arrow b, through a rotary shaft 116 connected to a turning drive which is not shown. In addition, the surface opposed to the polishing surface plate 111, of the polishing head 115 is so designed as to mount a work 301 thereon. As the method for mounting the work, various methods can be adopted, such as vacuum suction, electrostatic attraction, adhesion by use of an adhesive, adhesion by use of a pressure sensitive adhesive sheet, etc. Furthermore, a nozzle 121 for supplying a polishing slurry 131 (indicated by an arrow, for convenience) onto the polishing pad 1 is provided on the upper side of the polishing surface plate 111 and in the vicinity of the polishing head 115. The polishing slurry 131 is so supplied as to come between the polishing pad 1 and the work 301 as the polishing surface plate 111 is turned.
The first polishing method according to the present invention will be described below. As an example, the method of polishing by use of the above-described first polishing apparatus 101 will be described. First, a desired one of the polishing pads 1 to 4 is mounted on the polishing surface plate 111. In addition, the work 301 is mounted on the polishing head 115. Thereafter, the polishing slurry 131 is supplied from the nozzle 121 onto the polishing pad 1, and the polishing surface plate 111 is turned. Besides, the polishing head 115 is also turned. Then, the work 301 is brought into contact with the polishing pad 1 so as to obtain a desired processing pressure, whereby the surface to be polished of the work 301 is polished. As an example of the polishing conditions, a potassium hydroxide (KOH)-based fumed silica slurry was used as the polishing slurry 131, the processing pressure was set at 300 g/cm², and the rotating speeds were so set that the circumferential speed of the polishing pad relative to the work (e.g., wafer) was 60 m/min. After the polishing is finished, the work 301 is separated from the polishing pad 1, the supply of the polishing slurry 131 is stopped, and the turnings of the polishing surface plate 111 and the polishing head 115 are stopped. Thereafter, the work 301 may be detached from the polishing head 115. Incidentally, the polished surface of the work 301 may be washed before the detachment.
The second polishing apparatus is a belt-type polishing apparatus for polishing a surface to be polished of a material to be polished, by bringing a polishing pad into contact with the surface and into a frictional motion relative to the surface, wherein the polishing apparatus comprises one of the above-described polishing pads 5 and 6.
Specifically, as shown in FIG. 8, the second polishing apparatus 201 comprises turnable rollers 211 and 212 disposed in parallel to each other, and the polishing pad 5 or 6 described above referring to FIG. 5 or 6 of the belt type which is wrapped around the rollers 211 and 212. Here, as an example, the polishing pad 5 is used. Description will be made below referring to the polishing pad 5. The polishing pad 5 is stretched in a deflection-free state by the rollers 211 and 212. In addition, it is preferable to provide, between the rollers 211 and 212, a guide (not shown) which is for preventing the polishing pad from deflecting toward the inside, i.e., for internally supporting the polishing pad toward the polishing head 215 and on which the polishing pad can be freely slid. Besides, at least either one of the rollers 211 and 212 turned by a turning drive in the direction of arrow c, for example. This turns the polishing pad 4 in the direction of arrow d.
A polishing head 215 is provided opposite to the polishing surface of the polishing pad 5. The polishing head 215 is designed to be freely raised and lowered. Further, the polishing head 215 is turned through a rotary shaft 216 connected to a turning drive which is not shown. In addition, the surface opposed to the polishing pad 5, of the polishing head 215 is so designed as to mount a work 301 thereon. As the method for mounting the work 301, a variety of methods can be adopted, such as vacuum suction, electrostatic attraction, adhesion by use of an adhesive, adhesion by use of a pressure sensitive adhesive sheet, etc. Furthermore, a nozzle 221 for supplying a polishing slurry 231 (indicated by an arrow, for convenience) onto the polishing pad 5 is provided on the upper side of the polishing pad 5 and in the vicinity of the polishing head 215. The polishing slurry 231 is so supplied as to come between the polishing pad 5 and the work 301 as the rollers 211 and 212 are turned.
The second polishing method according to the present invention will be described below. As an example, the method of polishing by use of the above-described second polishing apparatus 201 will be described. First, a desired one of the polishing pads 5 and 6 is selected. Here, the polishing pad 5 is used. Therefore, description will be made below referring to the polishing pad 5. In addition, a work 301 is mounted on the polishing head 215. Thereafter, the polishing slurry 231 is supplied from the nozzle 221 onto the polishing pad 5, and the rollers 211 and 212 are turned to turn the polishing pad 5. Besides, the polishing head 215 is also turned. Then, the work 301 is brought into contact with the polishing pad 5 so as to obtain a desired processing pressure, whereby the surface to be polished of the work 301 is polished. As an example of polishing conditions, a potassium hydroxide (KOH)-based fumed silica slurry was used as the polishing slurry 231, the processing pressure was set at 300 g/cm², and the rotating speeds were so set that the circumferential speed of the polishing pad relative to the work (e.g., wafer) was 60 m/min. After the polishing is over, the work 301 is separated from the polishing pad 5, the supply of the polishing slurry 231 is stopped, and the turnings of the polishing pad 5 (the rollers 211 and 212) and the polishing head 215 are stopped. Thereafter, the work 301 may be detached from the polishing head 215. Incidentally, the polished surface of the work 301 may be washed before the detachment.
The above-described polishing methods are mere examples, and the polishing conditions can be appropriately modified according to the object of polishing. In addition, conventionally used polishing conditions may also be used.
As has been described above, according to the first polishing pad of the present invention, the polishing pad is provided with a plurality of slots piercing through the polishing pad in the thickness direction, so that it is possible to lower the hermetic seal property between the surface to be polished and the polishing pad surface, thereby ensuring that a negative pressure is less liable to be generated there. Therefore, the work can be easily removed from the polishing pad surface after completion of polishing. In addition, since the slots can be formed by punching, the polishing pad is lower in production cost than a related-art polishing pad provided with grooves formed by a related-art cutting operation. Further, since the slots are so formed as to pierce through the polishing pad in the thickness direction, the slots are not lost even when the polishing pad is worn, so that the polishing pad can show a prolonged pad life, as compared with the polishing pads provided with grooves.
According to the second polishing pad of the present invention, the polishing pad is provided with a plurality of holes piercing through the polishing pad in the thickness direction, and part of the plurality of holes are composed of slots, so that the same effects as those of the first polishing pad can be obtained. Further, since a plurality of holes other than the slots are present, it is possible to prevent the polishing resistance from increasing. Furthermore, since the slots can reserve the polishing liquid therein, the amount of the polishing liquid used can be reduced, as compared to the cases of the grooved polishing pads according to the Related Art. In addition, since the plurality of holes inclusive of the slots can be formed by a single punching operation, the production cost of the polishing pad is lowered, as compared with the cases of the related-art polishing pads provided with grooves by cutting. Furthermore, since the slots are so formed as to pierce through the polishing pad in the thickness direction, the slots are not lost even when the polishing pad is worn, so that the polishing pad can show a prolonged pad life, as compared with the polishing pads provided with grooves.
According to the polishing apparatuses of the present invention, the operating cost of the polishing apparatus can be lowered, since the polishing pad according to the present invention which can be produced at a lower cost is mounted thereon. Further, since the polishing pad according to the present invention is longer in pad life than the grooved polishing pads according to the Related Art, it is possible to lower the frequency of replacement of the polishing pad. As a result, the operating cost of the polishing apparatus can be lowered. In addition, it is possible to obtain the functions and effects of the polishing pads according to the present invention.
The polishing method according to the present invention promises a reduction in polishing cost, since the polishing pad according to the present invention which can be produced at a lower cost is used in the method. Furthermore, since the polishing pad according to the present invention is longer in pad life than the related-art polishing pads provided with grooves, it is possible to reduce the frequency of replacement of the polishing pad. As a result, polishing cost can be reduced. In addition, the functions and effects of the polishing pads according to the present invention can be obtained.

Claims

1-18. (canceled)

19. A method of forming a polishing pad for polishing a surface of a material to be polished, comprising:

providing a polishing pad; and

forming slots in the polishing pad which extend through the entire thickness of said polishing pad in the thickness direction such that the slot opening on one surface of the pad is substantially the same size and shape as the slot opening on the opposing surface of the pad, and wherein the slots do not extend to an outer circumferential surface of the pad.

20. A method of forming a polishing pad for polishing a surface of a material to be polished, comprising:

providing a polishing pad; and

forming holes in the polishing pad which extend through the entire thickness of said polishing pad in the thickness direction, part of said plurality of holes being composed of slots and wherein the slots do not extend to an outer circumferential surface of the pad, and wherein each slot opening on one surface of the pad is substantially the same size and shape as the slot opening on the opposing surface of the pad.

21. A method of forming a polishing pad as set forth in claim 20, wherein the holes and the slots do not overlap.

22. A method of forming a polishing pad as set forth in claim 19, wherein the formation of the slots in the polishing pad is comprised of punching the slots into the polishing pad.

23. A method of forming a polishing pad as set forth in claim 20, wherein the formation of the slots in the polishing pad is comprised of punching the slots into the polishing pad.