U.S. patent application number 10/830678 was filed with the patent office on 2004-10-07 for turning tool for grooving polishing pad, apparatus and method of producing polishing pad using the tool, and polishing pad produced by using the tool.
This patent application is currently assigned to Toho Engineering Kabushiki Kaisha. Invention is credited to Suzuki, Tatsutoshi.
Application Number | 20040198199 10/830678 |
Document ID | / |
Family ID | 21832215 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040198199 |
Kind Code |
A1 |
Suzuki, Tatsutoshi |
October 7, 2004 |
Turning tool for grooving polishing pad, apparatus and method of
producing polishing pad using the tool, and polishing pad produced
by using the tool
Abstract
Disclosed is a turning tool for cutting circumferential grooves
into a surface of a polishing pad formed of a resin material and
utilized for polishing semiconductor devices. The turning tool
comprising a cutting part arranged to have a tooth width within a
range of 0.005-1.0 mm, a wedge angle within a range of 15-35
degrees, and a front clearance angle within a range of 65-45
degrees. A polishing pad effectively formed by using the turning
tool, and an apparatus and a method of producing such a polishing
pad by utilizing the turning tool are also disclosed.
Inventors: |
Suzuki, Tatsutoshi;
(Yokkaichi-shi, JP) |
Correspondence
Address: |
Marc A. Rossi
ROSSI & ASSOCIATES
P.O. Box 826
Ashburn
VA
20146-0826
US
|
Assignee: |
Toho Engineering Kabushiki
Kaisha
|
Family ID: |
21832215 |
Appl. No.: |
10/830678 |
Filed: |
April 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10830678 |
Apr 23, 2004 |
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10026504 |
Dec 19, 2001 |
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Current U.S.
Class: |
451/242 |
Current CPC
Class: |
B23B 2210/022 20130101;
B23B 2251/50 20130101; B24B 37/26 20130101; B23B 2220/12 20130101;
B23Q 1/52 20130101; B23Q 16/04 20130101; Y10T 407/2206 20150115;
B24D 18/00 20130101; Y10T 407/25 20150115; Y10T 83/0304 20150401;
Y10T 407/23 20150115; Y10T 29/49995 20150115; Y10T 29/5168
20150115; B23B 2210/02 20130101; B23C 5/08 20130101; B23C 5/10
20130101; B23B 27/04 20130101; Y10T 407/2208 20150115; Y10T
407/2202 20150115; Y10T 82/10 20150115 |
Class at
Publication: |
451/242 |
International
Class: |
B24B 049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 1999 |
JP |
11-194646 |
Claims
What is claimed is:
1. A turning tool for cutting circumferential grooves into a
surface of a polishing pad formed of a resin material and utilized
for polishing semiconductor devices, said turning tool comprising:
a cutting part arranged to have a tooth width within a range of
0.005-1.0 mm, a wedge angle within a range of 15-35 degrees, and a
front clearance angle within a range of 65-45 degrees.
2. A turning tool according to claim 1, wherein said cutting part
has a rake angle within a range of 20-10 degrees.
3. A turning tool according to claim 1, wherein said cutting part
has a side clearance angle with respect to a radially outer wall of
each of said grooves, which is held within a range of 0-3
degree.
4. A turning tool according to claim 1, wherein said turning tool
includes a plurality of cutting parts which are arranged in a
predetermined direction with a pitch within a range of 0.2-2.0
mm.
5. A turning tool according to claim 4, wherein said plurality of
cutting parts are arranged in a predetermined direction with
regular pitches.
6. A turning tool according to claim 4, further comprising a
plate-like shaped tool tip having a plurality of cutting parts
integrally formed at one of edge portions thereof so as to protrude
outwardly from said one of said edge portions.
7. A turning tool according to claim 6, wherein said turning tool
comprising a plurality of said tool tips, said tool tips being
fixedly arranged with each other so as to be aligned in a width
direction thereof, said cutting parts of said plurality of tool
tips cooperate to form a multiplicity of cutting parts.
8. A turning tool according to claim 7, further comprising a
predetermined tool-tip holder to which said plurality of said
plate-like shaped tool tips are detachably fixed, said tool tip
holder and said plurality of tool tips cooperate to constitute a
tool unit.
9. A turning tool according to claim 4, further comprising a
plurality of cutting tips each having one of said cutting parts,
said plurality of cutting tips are detachably fixed to each other
so that cutting parts of said plurality of cutting tips cooperate
to form a plurality of cutting parts.
10. A turning tool according to claim 9, wherein said plurality of
cutting tips are superposed on and integrally fixed to one another
with spacers interposed adjacent ones of the cutting tips so that
the spacers function to keep a pitch of said plurality of cutting
tips.
11. A turning tool according to claim 9, further comprising a
cutting-tip holder to which the plurality of cutting tips are
detachably fixed, said cutting tip holder and said cutting tips
cooperate to constitute a unit tool.
12. A turning tool according to claim 10, further comprising a
cutting-tip holder to which the plurality of cutting tips are
detachably fixed, said cutting tip holder and said cutting tips
cooperate to constitute a unit tool.
13. A turning tool according to claim 1, wherein said cutting part
has a tip portion arcuately curved in a width direction thereof so
that said tip portion has two end parts opposed in said width
direction, said two end parts of said tip portion protruding
outwardly from an intermediate part of said tip portion in a
direction perpendicular to said width direction.
14. A turning tool according to claim 1, wherein said cutting part
has a tip portion being serrated.
15. A turning tool according to claim 1, wherein said cutting part
has at least one side surface being serrated.
16. A method of producing a polishing pad made of a resin material,
comprising the steps of: positioning a turning tool comprising a
cutting part arranged to have a tooth width within a range of
0.005-1.0 mm, a wedge angle within a range of 15-35 degrees, and a
front clearance angle within a range of 65-45 degrees, relative to
a base for said polishing pad formed of said resin material;
rotating said cutting part of said turning tool relative to said
base for said polishing pad about an axis of said base for said
polishing pad, for cutting circumferential grooves into a surface
of said base such that radially inner most one of said
circumferential grooves has a radius of curvature of 10 mm or
smaller.
17. A method of producing a polishing pad according to claim 16,
wherein said turning tool comprises a plurality of cutting parts
which are arranged in a predetermined direction with a pitch within
a range of 0.2-2.0 mm, and wherein said circumferential grooves
comprises a multiplicity of generally concentric annular grooves,
said method further comprising the steps of: simultaneously cutting
a plurality of said generally concentric grooves into said surface
of said base for said polishing pad such that radially inner most
one of said multiplicity of generally concentric annular grooves
has a radius of curvatures of 10 mm or smaller.
18. A method of producing a polishing pad according to claim 17,
wherein said plurality of cutting parts are arranged in a
predetermined direction with regular pitches.
19. A method of producing a polishing pad according to claim 16,
wherein said turning tool comprises a plate-like shaped tool tip
having a plurality of cutting parts integrally formed at one of
edge portions thereof so as to protrude outwardly from said one of
said edge portions and arranged in a predetermined direction with a
pitch within a range of 0.2-2.0 mm, and wherein said
circumferential grooves comprises a multiplicity of generally
concentric annular grooves, said method further comprising the
steps of: simultaneously cutting a plurality of said generally
concentric grooves into said surface of said base for said
polishing pad such that radially inner most one of said
multiplicity of generally concentric annular grooves has a radius
of curvatures of 10 mm or smaller.
20. A method of producing a polishing pad according to claim 19,
wherein said turning tool comprises a plurality of said plate-like
shaped tool tips, said tool tips being fixedly arranged with each
other so as to aligned in a width direction thereof such that said
cutting parts of said tool tips cooperate to form a multiplicity of
cutting parts.
21. A method of producing a polishing pad according to claim 20,
wherein said turning tool further comprises a predetermined
tool-tip holder to which said plurality of said plate-like shaped
tool tips are detachably fixed, said tool tip holder and said
plurality of tool tips cooperate to constitute a tool unit.
22. A method of producing a polishing pad according to claim 16,
wherein said turning tool comprises a plurality of cutting tips
each having a cutting part and detachably fixed to each other so
that cutting parts of said plurality of cutting tips cooperate to
form a plurality of cutting parts which are arranged in a
predetermined direction with a pitch within a range of 0.2-2.0 mm,
and wherein said circumferential grooves comprises a multiplicity
of generally concentric annular grooves, said method further
comprising the steps of: simultaneously cutting a plurality of said
generally concentric grooves into said surface of said base for
said polishing pad such that radially inner most one of said
multiplicity of generally concentric annular grooves has a radius
of curvatures of 10 mm or smaller.
23. A method of producing a polishing pad according to claim 16,
wherein said turning tool is adapted to cut said circumferential
grooves into said surface of said base for said polishing pad at a
feed per revolution of 0.005-0.05 mm/rev in a depth direction of
said base.
24. A method of producing a polishing pad according to claim 16,
further comprising the steps of: blowing ionic fluid toward a
vicinity of said cutting parts to neutralize said base of said
polishing pad and chips which are electrically charged due to
execution of said step of cutting by the turning tool said
circumferential grooves into said surface of said base for said
polishing pad.
25. A polishing pad comprising: a base made of a resin material;
and circumferential grooves open in a surface of said base, said
grooves having a width within a range of 0.005-1.0 mm, a depth of
0.2-2.0 mm, and a pitch of 0.2-2.0 mm, wherein radially inner most
one of said circumferential grooves has a radius of curvature of
not larger than 10 mm.
26. A polishing pad according to claim 25, wherein radially outer
most one of said grooves has a radius of curvature of not less than
100 mm.
27. A polishing pad according to claim 25, wherein said radially
inner most one of said grooves has a radius of curvature of not
larger than 10 mm, and said polishing pad has a diameter which is
made smaller than that of a working piece.
28. A polishing pad according to claim 25, wherein said
circumferential grooves are spaced apart from each other at uniform
pitch.
29. A polishing pad according to claim 25, wherein said base is a
rigid urethane foam member, and said multiplicity of generally
concentric grooves are formed with a width of 0.20-0.30 mm, a depth
of 0.1-1.0 mm and a pitch of 1.0-2.0 mm.
30. A polishing pad according to claim 25, wherein said polishing
pad is usable for polishing a substrate of multilevel
interconnection type in which is formed an interconnect line having
a width of 0.18 .mu.m.
31. A polishing pad according to claim 25, wherein said polishing
pad is adapted to be directly placed on a platen of a polishing
device for polishing semiconductor devices, without needing an
elastic layer interposed therebetween.
32. A machine for grooving a base for a polishing pad made of a
resin material, said machine comprising: a bed; a platen including
a hollow shaft member supported by said bed via bearing so that
said hollow shaft member is rotatably about a C-axis which is
perpendicular to said bed; a suction plate fixed to one of opposite
axial end portions of said hollow shaft member remote from said bed
and formed with a plurality of through holes arranged evenly over
an entire area thereof for attracting the base for the polishing
pad to be placed on said suction plate; drive mechanism for
rotating said platen about said C-axis and for positioning said
platen at a suitable angular position; a gate-shaped column having
two legs which are opposed to each other with a spacing
therebetween and a cross rail extending between and being
perpendicular to said two legs, said gate-shaped column being
movable in a direction of an X-axis with said cross rail extending
across said platen; at least one saddle mounted on said cross rail
so as to be movable in a direction of a Y-axis extending along said
cross rail; a tool rest mounted on said saddle so as to be
independently reciprocally movable in a direction of a Z-axis, said
tool rest adapted to detachably hold a fixed tool comprising a
turning tool comprising a cutting part arranged to have a tooth
width within a range of 0.005-1.0 mm, a wedge angle within a range
of 15-35 degrees, and a front clearance angle within a range of
65-45 degrees; drive motors for moving and positioning said platen,
said column and said saddle and said tool rest; and a numerical
control apparatus totally control an operation of said drive motor,
wherein said hollow shaft member of said platen is connectable to
an air suction device so as to attract said base for said polishing
pad on said suction plate by a suction force applied from said air
suction device to said base for said polishing pad, and wherein
said machine being operable to cut by said turning tool a
multiplicity of generally concentric annular grooves into a surface
of said base for said polishing pad with said base for said
polishing pad being attracted on said suction plate.
33. A machine according to claim 32, further comprising: an
ion-blowing device for neutralizing said static electricity charged
in said polishing pad and chips, for separating said chips from
said fixed tool and said polishing pad, wherein said ion blowing
device includes an ion generating device for generating ion, an ion
extruding nozzle for extruding said ion toward said cutting part of
said fixed tool, an air blowing device for blowing air together
with said ion.
34. A machine according to claim 32, wherein said tool rest
detachably supports a rotative tool selected from a group
consisting of a milling cutter unit and a drill unit.
35. A machine according to claim 32, wherein said milling cutter
unit including at least one milling cutter fixedly supported by a
tool shaft extending along a center axis thereof, said at least one
cutter including a disk-shaped body member and a plurality of
cutting edges disposed at an outer peripheral portion of said body
member at regular angular intervals, and each having a wedge angle
within a range of 20-40 degrees, and a front clearance within a
range of 30-45 degrees, a tooth width within a range of 0.3-2.0 mm,
and a side cutting edge angle of 0-2 degree.
36. A machine according to claim 35, wherein said machine comprises
a plurality of said milling cutters which are fixedly disposed onto
said tool shaft such that said tool shaft extend through center
axes of said plurality of said milling cutters and said plurality
of milling cutters are spaced apart from each other in an axial
direction of said tool shaft at a uniform pitch of 0.1 or more.
37. A machine according to claim 34, wherein said drill unit
comprises a single-spindle type or a multiple-spindle type drill
unit, said drill unit including a drill having a drill diameter of
0.5-1.5 mm, a drill length of 20-30 mm two cutting edges of helix
angle of 1-10 degrees, said drill being a straight drill having no
back-tapered portion at cutting edges thereof and having a shape
edge that has a conical angle with no chisel portion of 55-65
degrees.
38. A machine according to claim 32, further comprises a sequential
control device adapted to control operation of said drive motor in
place of said numerical control apparatus.
39. A machine according to claim 32, wherein said machine includes
two of said saddles, wherein at least one of said tool holders of
said two saddles is adapted to detachably support said fixed tool
comprising said turning tool comprising a cutting part arranged to
have a tooth width within a range of 0.005-1.0 mm, a wedge angle
within a range of 15-35 degrees, and a front clearance angle within
a range of 65-45 degrees, and an other one of said tool holders of
said two saddles is adapted to detachably support said rotative
tool selected from a group consisting of said milling cutter unit
and said drilling unit.
40. A machine according to claim 32, wherein said machine includes
only one said saddle, said tool holder being adapted to
interchangeably support said fixed tool comprising the turning tool
comprising a cutting part arranged to have a tooth width within a
range of 0.005-1.0 mm, a wedge angle within a range of 15-35
degrees, and a front clearance angle within a range of 65-45
degrees, or said rotative tool selected from a group consisting of
said milling cutter unit and said drilling unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a turning tool for
producing a polishing pad made of a resin material and usable in
the fabrication of semiconductor devices, especially for chemical
mechanical polishing (CMP) executed for planaraizing surfaces of
semiconductor wafers or devices. The present invention further
relates to a polishing pad effectively formed by using the turning
tool, and an apparatus and a method of producing such a polishing
pad by utilizing the turning tool.
[0003] 2. Description of the Related Art
[0004] In the semiconductor fabrication processes, a substrate,
e.g., a silicon wafer, may undergo multiple masking, etching,
implantation, and dielectric and conductor deposition processes, to
thereby form a lamination of various kinds of thin layers such as
metallic layers and insulative layers. Between each processing
steps, it is usually necessary to polish or planarize an outer or
upper most surface of the wafer to obtain a substrate surface
having a high degree of planarity. Chemical mechanical polishing
(hereinafter referred to as "CMP") is one of known methods of
planarization. CMP typically involves placing the wafer mounted on
and rotated about an axis of a carrier against a polishing pad
mounted on and rotated about an axis of a platen, and pushing the
wafer against the polishing pad while supplying a polishing slurry
at an interface between the upper most surface of the wafer and the
polishing pad. The polishing slurry consists of fine abrasive
particles and suitable kind of liquid in which the abrasive
particles are dispersed. Typically, the polishing pad is made of a
foamed rigid-resin material, so that a surface of the polishing pad
has a cellular structure of independent-cell type in which cells
are independent of each other or of open-cell type in which cells
are communicated with each other, in order to facilitate
conditioning of the slurry distribution between the wafer and the
polishing pad.
[0005] Namely, the polishing pad for CMP is required to be capable
of evenly distributing the slurry over a substantially entire area
of the upper most surface of the wafer that is to be polished,
while preventing a stay or clogging of the slurry at a local
portion of the upper most surface of the wafer. The polishing pad
for CMP is further required to be capable of promoting renewal of
the slurry.
[0006] To meet these requirements, conventionally employed
polishing pads for CMP are arranged to have polishing surfaces
formed with respective predetermined patterns, e.g., a pattern of
recess or a pattern of checked grooves intersecting at right
rights. After a number of polishing runs, the polishing pad having
the pattern of recesses may suffer from variation of diameter of
the recesses, whereby the pad suffers from difficulty in exhibiting
a desired chemical mechanical polishing effect with high stability.
In the case of the polishing pad having the pattern of checked
grooves, a polishing condition is likely to vary in the radial
direction of the polishing pad, whereby the pad suffers from a high
tendency of occurrence of uneven wearing of its surface, resulting
in uneven polishing.
[0007] Another known example of conventionally employed polishing
pad for CMP is disclosed in US Patent Publication Nos. U.S. Pat.
No. 5,921,855 and U.S. Pat. No. 5,984,769. The disclosed polishing
pad is provided with a plurality of annular grooves open in its
polishing surface. The plurality of annular grooves are arranged in
a generally concentric or coaxial relationship with each other, and
are dimensioned to have a width of not smaller than 0.38 mm and a
depth of not smaller than 0.51 mm, and are uniformly spaced with a
pitch of 2.29 mm in a radial direction of the polishing pad.
However, the disclosed polishing pad suffers from inherent
structural problems, namely, difficulty in forming grooves
extending in a circumferential direction in the polishing pad and
difficulty in ensuring a sufficient dimensional accuracy of the
grooves.
[0008] More specifically described, the annular grooves may be
formed on the polishing surface of the polishing pad by embossing
with a die, or alternatively may be formed by milling with a saw
blade on a mill. In the former case, each of the formed annular
grooves is prone to have a dull shape, especially at its open-end
edge portions, so that the width of the groove varies in its depth
direction. This causes undesirable variation of the groove width,
especially when the polishing surface of the polishing pad is worn
or is conditioned by the dressing process, resulting in unstable
polishing conditions. In the latter case, since the annular grooves
are formed by milling of the saw blade on the mill, the formed
annular grooves is likely to extend straightly to some extent,
making it difficult to form a groove having a small width and a
small radius of curvature. This makes it impossible to form a
desired polishing pad in which annular grooves having a relatively
small width are formed on a radially inner portion of its polishing
surface as well as a radially intermediate and a radially outer
portion of its polishing surface. In view of a recent tendency of
employing a large-diameter wafer, e.g., a wafer having a diameter
within a range of 200 mm-300 mm or more, the presence of useless
area in the radially inner portion of the polishing surface of the
polishing pad undesirably causes an enlargement in size of the
polishing pad. Therefore, the problem of the radially inner useless
area of the polishing pad becomes very significant.
[0009] Alternatively, the annular grooves may possibly be formed by
turning with a turning tool. However, since the polishing pad is
formed of a specific material having somewhat elasticity, e.g., a
foamed rigid-resin material, it is significantly difficult to cut
an annular groove having a relatively small width and having a
relatively small radius of curvature into the polishing pad, with
high dimensional accuracy. In the light of the physical property of
the polishing pad, conventionally available tool for cutting a work
piece made of metal or a rigid-resin material, are not suitable to
cut the polishing pad. For instance, the tools for cutting the
metallic or rigid-resin working piece are likely to interfere with
the walls of each groove, thereby possibly producing burrs or other
defects in the walls of the grooves. Thus, the conventionally
available tools are incapable of cutting the small-width and
small-radius grooves into the surface of the polishing pad having
the somewhat elasticity, like the foamed rigid-resin members.
[0010] Moreover, the conventionally employed polishing pad
disclosed in the above-mentioned U.S. Patents has the generally
concentric annular grooves that have a relatively large width and
are uniformly spaced at the relatively large pitch. Further, the
disclosed polishing pad includes a backside pad made of a
compressed felt fibers leached with urethane, which has an
elasticity larger than that of the polishing pad and which is fixed
the backside of the urethane pad. Thus, the disclosed polishing pad
is mounted on a platen of an optional CMP system via the backside
pad. This type of conventional polishing pad has been developed to
be applied to planarization of a substrate having multilevel
interconnections in which metallic interconnect has a width of 0.25
cm, that is a most advanced technology at the time when
applications for the above-mentioned U.S. Patents were filed (i.e.,
1997-1998). Namely, the type of polishing pad has been developed to
provide the substrate surface having a planarity at a level of 0.3
.mu.m. In the light of the fact that the substrates having
multilevel interconnections whose metallic interconnect has a width
approximately of 0.18 .mu.m, 0.15 .mu.m and 0.1 .mu.m dominate the
recent market, it is apparent that the CMP is now required very
sophisticated techniques, i.e., to provide the substrate surface
having a high planarity at a level of 0.25 .mu.m or lower. Thus,
the conventional polishing pad disclosed in the above U.S. Patents
is insufficient for ensuring currently required polishing accuracy
and polishing efficiency, and accordingly is unsuitable to be used
for CMP for a planarization of a currently developed substrate of
multilevel interconnection, which includes interconnect metal
layers made of a soft cupper or gold.
[0011] In the conventional polishing pad disclosed in the
above-indicated U.S. Patents, the grooves having a relatively large
width and the backside pad cooperate to allow a deformation of the
polishing surface, whereby the polishing surface of the polishing
pad is likely to be deformed according to peaks and valleys in a
surface of a substrate to be polished, i.e., along with topography
of upper most surface of the substrate. However, this surface
deformation mechanism of the conventional polishing pad is
insufficient to keep pace with the currently required level of
polishing accuracy. In addition, the use of the backside pad, which
is formed differently from the polishing pad, evidently has pushed
up a manufacturing cost of the polishing pad.
SUMMARY OF THE INVENTION
[0012] It is therefore a first object of the invention to provide a
novel turning tool for cutting circumferential grooves, e.g., a
multiplicity of generally concentric annular grooves into a surface
of a polishing pad formed of a resin material and utilized for
polishing semiconductor devices. The turning tool is capable of
forming the fine circumferential grooves with a sufficiently small
width and with high dimensional accuracy and high stability. The
turning tool enables to form the small-width circumferential
grooves in the radially inner portion of the polishing surface of
the polishing pad, with ease.
[0013] It is a second object of the invention to provide a novel
method of producing a polishing pad formed of a resin material and
usable for polishing semiconductor devices, by utilizing a special
turning tool constructed according to the present invention. The
method enables to form circumferential grooves, e.g., a
multiplicity of generally concentric annular grooves on a surface
of the polishing pad with a sufficiently small width and with high
dimensional accuracy and high stability, over a sufficiently wide
area of the surface of the polishing pad including a radially inner
portion of the surface of the polishing pad.
[0014] It is a third object of the invention to provide a polishing
pad formed of a resin material and usable for polishing
semiconductor devices, which is novel in construction, which is
suitably produced by using a special turning tool specific working
tool constructed according to the present invention, and which is
effectively usable for chemical mechanical polishing of a substrate
of multilevel interconnection structure in which a width of a
metallic interconnection is set to about 0.1 .mu.m.
[0015] It is a fourth object of the invention to provide a machine
for forming grooves on a polishing pad, which is novel in
construction, which utilizes a special turning tool constructed
according to the present invention, and which is capable of easily
cutting circumferential grooves e.g., a multiplicity of
circumferential annular grooves into a surface of the polishing pad
such that the grooves have a relatively small width and spaced
apart from each other with a relatively small radial pitch.
[0016] The above and/or other objects may be attained according to
at least one of the following aspects of the invention. The
following preferred forms of the respective aspects of the
invention may be adopted at any possible optional combinations. It
is to be understood that the present invention is not limited to
the following forms or combinations of these forms, but may
otherwise be recognized based on the thought of the present
invention that described in the whole specification and drawings or
that may be recognized by those skilled in the art in the light of
the disclosure in the whole specification and drawings.
[0017] The above-indicated first object of the invention may be
achieved according to a first aspect of the invention which
provides a turning tool for cutting circumferential grooves into a
surface of a polishing pad formed of a resin material and utilized
for polishing semiconductor devices, the turning tool comprising: a
cutting part arranged to have a tooth width within a range of
0.005-1.0 mm, a wedge angle within a range of 15-35 degrees, and a
front clearance angle within a range of 65-45 degrees.
[0018] The turning tool of the invention comes into fruition as a
result of a large number of experiments and extensive studies on
grooving of a polishing pad made of a resin material, which were
conducted by the inventor of the present invention. In particular,
the turning tool of the invention has been developed as a special
turning tool capable of cutting desired fine grooves with high
dimensional accuracy into the polishing pad made of the resin
material in both of a solid state and a foamed state. One of the
significant technical features of the turning tool of the present
invention is that the wedge angle which is made significantly shape
in comparison with general turning tools adapted to cut metallic
work pieces, and the front clearance angle is made sufficiently
larger than that of the general turning tools. Although such a
general turning tool adapted to cut metallic work piece may be used
for cutting work pieces made of rigid synthetic resin materials,
such as engine plastics, polyamide resin, and the like, the general
turning tool is not able to process with sufficient dimensional
accuracy the polishing pad made of the resin material whose
hardness is smaller than those of the rigid-synthetic resin
materials. This clearly shows significant difficulty or specialty
in cutting the circumferential grooves into the polishing pad made
of the resin material. In particular, the present turning tool
enables to cut fine circumferential grooves with high dimensional
accuracy into such a polishing pad made of a foamed rigid-resin
material, e.g., a foamed urethane pad, and a polishing pad made of
a solid resin material whose hardness is generally similar to that
of the polishing pad formed of the foamed rigid-resin material.
[0019] The turning tool constructed according to the present
invention is capable of cutting into the polishing pad made of the
resin material the circumferential grooves having a width of 1.0 mm
or smaller, with high dimensional accuracy and without occurrence
of burrs in the walls of the grooves. Namely, the turning tool of
the present invention makes it possible to stably cut the
circumferential grooves into the surface of the polishing pad with
a slight infeed rate, and to accurately form the desired grooves in
the very inner circumferential portion of the circular work piece.
It should be appreciated that the term "circumferential grooves"
should be interpreted to mean grooves extending in a
circumferential direction of the polishing pad, e.g., a
multiplicity of generally annular generally concentric grooves, and
a spiral groove or grooves. Preferably, the tooth width is held
within a range of 0.1-1.0 mm.
[0020] The turning tool constructed according to the present
invention may be made of known materials such as hard metal, high
speed steel, carbon steel, ceramics, cermet, and diamonds. In the
turning tool of the present invention, actual values of the wedge
angle and the front clearance angle may be suitably determined
within the above-indicated range, taking into account a hardness or
other specific physical properties of the work piece, i.e., the
polishing pad made of the resin material. It is noted that, if the
wedge angle of the turning tool is set to 15 degrees or smaller,
the life of the turning tool is shorten, although the cutting
ability of the tool is improved. If the wedge angle of the turning
tool is set to 35 degrees or larger, the cutting ability of the
tool is deteriorated, resulting in a high possibility of occurrence
of defects, such as burrs, in the surface of the grooves. The
turning tool of the present invention has the wedged angle arranged
within a range of 15-35 degrees, thus making it possible to produce
a fine cutting into the polishing pad formed of the solid resin
material or the foamed rigid-resin material. Therefore, the turning
tool of the present invention is capable of preventing occurrence
of burrs on the surface of the grooves, while assuring high
processing accuracy. It is also noted that if the front clearance
angle of the turning tool is set to 45 degrees or smaller in the
case where the cutting grooves have relatively small radius of
curvatures, the side surfaces of the cutting part of the turning
tool is likely to interface with the radially outer walls of the
cutting grooves. This results in deterioration of a dimensional
accuracy of the grooves, due to occurrence of burrs, recesses
and/or protrusions in the surface of the groove walls, and dulled
open-end edges of the grooves. Further, the front clearance angle
of 65 degrees or larger may adversely effect on the life of the
cutting parts of the turning tool.
[0021] According to a first preferred form of the turning tool of
the invention, the cutting part of the turning tool has a rake
angle within a range of 20-10 degrees. It is noted that if the rake
angle is set to 20 degrees or larger, the cutting part of the
turning tool is prone to cut undesirably into the inside of the
polishing pad. On the other hand, if the rake angle is set to 10
degrees or smaller, the cutting ability of the turning tool is
deteriorated.
[0022] According to a second preferred form of the turning tool of
the invention, the cutting part has a side clearance angle with
respect to a radially outer wall of each of said grooves, which is
held within a range of 0-3 degrees. This arrangement enables to
prevent or avoid interface between the radially outer wall of each
groove and the cutting part of the turning tool with high
stability, thus making it possible to form the grooves with high
dimensional accuracy of its radially outer wall portion, even if a
radius of curvature of the groove is relatively small. An actual
values of the side clearance angle may be suitably determined
within the above-indicated range, taking into account a hardness or
other specific physical properties of the work piece, i.e., the
polishing pad made of the resin material, and the value of the
front clearance angle of the tool, so that the cutting part of the
turning tool is less likely to interface or cut into the radially
outer wall of the each groove. If the side clearance angle exceeds
3 degrees, durability or processability of the cutting part of the
tool may be deteriorated, so that the side clearance is preferably
set to 2 degrees or smaller. On the other hand, the side clearance
angle of the cutting part with respect to a radially inner wall of
each of the grooves can be set at around 0 degrees, since an
interfere between the cutting part of the turning tool and the
radially inner wall of the each groove is less likely to occur.
[0023] According to a third preferred form of the turning tool of
the invention, the turning tool includes a plurality of cutting
parts which are arranged in a predetermined direction with a pitch
within a range of 0.2-2.0 mm. The turning tool according to this
preferred form makes it possible to cut a plurality of generally
concentric grooves with a width within a range of 0.005-1.0 mm and
with a radial pitch of 0.2-2.0 mm with high efficiency. Preferably,
the cutting parts are arranged in a predetermined direction with a
generally constant pitch. According to the actual experiment
conducted by the inventor of the present invention, a tool having a
single cutting part according to the present invention needs one
hour or more for cutting an optional number of generally concentric
annular grooves into an optional base for the polishing pad, while
a multi edged tool having a plurality of cutting parts constructed
according to this preferred form of the turning tool of the
invention can do the same work in minuets. It should be appreciated
that such a multi-edged tool may be provided by utilizing a toll
tip or a plurality of tool tips each having a plurality of cutting
parts integrally formed thereon, or alternatively by utilizing a
plurality of cutting-part chips each having a single cutting part,
which are fixed together. Specific preferred form of the
multi-edged tool will be described hereinafter.
[0024] A first advantageous form of the multi-edged tool includes a
plate-like shaped tool tip having a plurality of cutting parts
integrally formed at one of edge portions thereof so as to protrude
outwardly from the one of the edge portions. Preferably, a
plurality of the tool tips are fixedly arranged with each other so
as to align in a width direction thereof so that the cutting parts
of the tool tips cooperate to form a multiplicity of cutting parts.
Yet preferably, the turning tool of the invention further comprises
a predetermined tool-tip holder to which the plurality of the
plate-like shaped tool tips are detachably fixed, so that the
tool-tip holder and the plurality of tool tips cooperate to
constitute a tool unit.
[0025] A second advantageous form of the multi-edged tool includes
a plurality of cutting tips each having one cutting part, and the
plurality of cutting tips are detachably fixed to each other so
that cutting parts of the plurality of cutting tips cooperate to
form a plurality of cutting parts. Preferably, the plurality of
cutting tips are superposed on and integrally fixed to one another
with spacers interposed adjacent ones of the cutting tips so that
the spacers function to keep a pitch of the plurality of cutting
tips. Preferably, the turning tool of the invention further
comprises a cutting-tip holder to which the plurality of cutting
tips are detachably fixed, so that the cutting-tip holder and the
cutting tips cooperate to constitute a unit tool.
[0026] According to a fourth preferred form of the turning tool of
the invention, the cutting part has a tip portion arcuately curved
in a width direction thereof so that the tip portion has two end
parts opposed in the width direction, wherein the two end parts of
the tip portion protrudes outwardly from an intermediate part of
the tip portion in a direction perpendicular to the width
direction.
[0027] In the turning tool according to the fourth preferred form,
the two end parts of the tip portion of the cutting part are
initially brought into contact with the polishing pad as the
working piece, upon a start of the cutting process. This
arrangement permits an excellent and smooth engagement of the
cutting part of the turning tool with the surface of the polishing
pad, even in the case where the polishing pad is formed of a
constrictive member, e.g., a solid resin member and a foamed
rigid-resin member, thus preventing undesirable dulling of the edge
in the open end portion of the formed groove, in other words,
undesirable increase of the width of the groove at the open end
portion of the groove. Therefore, a polishing pad having grooves
formed by using the cutting tool according to this preferred form
of the first aspect of the invention, is capable of ensuring a
desirable distribution of slurry, and does not suffer from
undesirable distribution of the slurry due to the presence of the
dulled edges in the open-end edge portions of the grooves. Further,
the smooth engagement of the cutting part of the turning tool of
this preferred from effectively prevent that a local portion of the
polishing pad is excessively compressed by the cutting part of the
cutting tool which is forcedly pressed thereon, in an attempt to
ensure the engagement of the cutting part with the surface of the
polishing pad, and is then damaged at a limiting point.
[0028] According to a fifth preferred form of the turning tool of
the invention, the cutting part has a tip portion being serrated.
Like the arcuately curved cutting part as described above, the
cutting part of this preferred form permits an excellent and smooth
engagement thereof with the surface of the polishing pad. In the
turning tool of this preferred form, it is desirable that a face, a
front clearance face and a tooth surface may be provided with a
fine polishing traces extending in one direction e.g., a turning
direction, or may be polished extremely smoothly, for thereby
facilitating flows of the cutting chips along these surfaces.
Preferably, the side surfaces of the cutting part of this turning
tool may be serrated.
[0029] The above-indicated second object of the invention may be
achieved according to a second aspect of the invention, which
provides a method of producing a polishing pad made of a resin
material, comprising the steps of: (a) positioning a turning tool
constructed according to the first aspect of the invention,
relative to a base for the polishing pad made of the resin
material; (b) rotating the cutting part of the turning tool and the
base for the polishing pad relative to each other about an axis of
the base for the polishing pad, so as to cut circumferential
grooves into a surface of the base, such that radially inner most
one of the circumferential grooves has a radius of curvature of 10
mm or smaller.
[0030] This method of the present invention makes it possible to
form by turning fine circumferential grooves having a relatively
small width into the base for the polishing pad made of a specific
material such as a solid resin material or a foamed rigid-resin
material, with high dimensional accuracy and ease. Moreover, the
present method enables to form such fine accurate grooves in a very
radially inner portion of the base for the polishing pad.
[0031] According to a first preferred form of the method of the
present invention, the turning tool is selected from the group of
consisting of the turning tools of the above-described third
preferred form of the first aspect of the invention, the first
advantageous form of the third preferred form of the first aspect
of the invention, and the second advantageous form of the third
preferred form of the first aspect of the invention, and the
circumferential grooves comprises a multiplicity of generally
concentric annular grooves, wherein the method further comprises
the steps of: (c) simultaneously cutting the multiplicity of
generally concentric annular grooves into the surface of the base
of the polishing pad such that the radially inner most one of said
multiplicity of generally concentric annular grooves has a radius
of curvature of 10 mm or smaller.
[0032] In this preferred form of the method of the invention, the
use of the specific multi-edged turning tools constructed according
to the present invention enables to form the multiplicity of fine
generally concentric annular grooves into the surface of the base
for the polishing pad with an accurate dimensioned pitch and with
high processing efficiency.
[0033] According to a second preferred form of the method of the
invention, the turning tool is adapted to cut the circumferential
grooves into the surface of the base for the polishing pad at a
feed per revolution of 0.005-0.05 mm/rev in a depth direction of
the base. This arrangement establish an excellent turning condition
for cutting the grooves by the present turning tool into the base
for the polishing pad which is made of a resin material in a solid
state or a foamed state, e.g., a foamed urethane pad. Since the
cutting of the grooves is performed at the above-indicated slight
feed per revolution, it is possible to sequentially cut the surface
of the base for the polishing pad without pressing the surface of
the base for the polishing pad. Further, this method permits a
smooth cutting of the fine circumferential grooves into the base
for the polishing pad with high stability, without any defects such
as undesirable cutting of the turning tool into the base and
occurrence of burrs in the surface of the formed grooves.
Preferably, the cutting parts and the base are rotated relative to
each other at a speed of 50-300 rev/min. It is noted that the speed
in the turning or cutting method according to the present invention
may be desirably determined, taking into account physical
properties of the base, quality of the cutting part and/or radius
of curvatures of grooves to be formed.
[0034] According to a third preferred form of the method of the
invention, the method further includes the step of blowing ionic
fluid toward a vicinity of the cutting parts to neutralize the base
for the polishing pad and chips which are electrically charged due
to execution of the step of cutting by the turning tool the
circumferential grooves into the surface of the base for the
polishing pad.
[0035] Upon cutting the base for the polishing pad made of the
resin material by the present turning tool, the base and the tool
are brought in frictional contact with each other, thus generating
static electricity having higher voltage. This may cause that the
chips are electrically charged and tend to adhere to the surface of
the base and cutting part or parts of the turning tool. To
eliminate this drawback, the ionic fluid is blown to the vicinity
of the cutting part(s), thus neutralizing the electrically charged
chips. This arrangement is effective to avoid undesirable damages
of the surface of the grooves due to the presence of the cutting
chips adhered to the surface of the grooves or cutting parts of the
tool. The blowing of the ionic fluid may be executed continuously
or discontinuously, or may be executed as needed. Preferably, the
ionic fluid is blown together with the compressed air, so that the
charged chips are neutralized and blown away from the surface of
the base for the polishing pad, simultaneously.
[0036] The above-indicated third object of the invention may be
achieved according to a third aspect of the invention, which
provides a polishing pad, which is effectively formed by using the
turning tool constructed according to a first aspect of the
invention, the polishing pad comprising: (a) a base made of a resin
material; and (b) circumferential grooves open in a surface of the
base, wherein the grooves have a width within a range of 0.005-1.0
mm, a depth of 0.2-2.0 mm, and a pitch of 0.2-2.0 mm, and wherein
radially inner most one of the circumferential grooves has a radius
of curvature of not larger than 10 mm.
[0037] In the polishing pad constructed according to the present
invention, the circumferential grooves have a relatively small
width and a sufficiently small pitch, in comparison with the known
polishing pads as disclosed in the above-indicated U.S. Patent
Publication Nos. U.S. Pat. No. 5,921,855 and U.S. Pat. No.
5,984,769. This specific structure of the polishing pad of the
present invention, which is distinguishable from that of the
conventional polishing pads, enables that the surface of the
polishing pad is deformed along a surface of a semiconductor
device, e.g., a wafer with improved accuracy, thus ensuring an
excellent surface polishing with high accuracy. Described more
specifically, the conventional polishing pad requires an elastic
backside pad fixed to the backside of a base for the conventional
polishing pad so as to absorb or compensate a relatively large
local deformation in the front surface of the base caused by
bending of grooved portions of the base. Namely, the wall thickness
of the base for the conventional polishing pad is decreased at the
grooved portion. Since the grooves have a relatively large width,
the grooved portion is likely to bent, resulting in the large local
deformation of the front surface of the base. Therefore, the
conventional polishing pad needs the elastic backside pad to be
deformed along the surface of the wafer with desired accuracy. On
the other hand, the polishing pad according to the present
invention is effectively arranged to sufficiently decrease a width
of partitions interposed between adjacent ones of the grooves and a
width of each groove, thereby minimizing an amount of local
deformation in the surface of the polishing pad due to bending of
the grooved portions, while allowing elastic deformation of the
partitions so as to expand toward the respective grooves disposed
opposite sides of the partitions (i.e., expand in its radially
opposite directions). This makes it possible that the surface of
the polishing pad is deformed along the surface of the wafer with
high accuracy, owing to the elastic deformations of the partitions,
thus ensuring a significantly high accurate polishing of the
semiconductor devices, that is never achieved by the conventional
polishing pad. The polishing pad of the present invention is
capable of suitably polishing semiconductor devices having
interconnects made of soft metallic materials and arranged with a
slight spacing therebetween. For instance, the polishing pad of the
present invention enables for the first time to polish and
planarize a substrate having multilevel interconnections whose
interconnect line has a width of 0.18 .mu.m, 0.15 .mu.m and/or 0.1
.mu.m, with a high planarity level of 0.25 .mu.m or lower.
[0038] Further, the polishing pad constructed according to the
present invention can eliminate the need for the backside pad that
is essentially required in the conventional polishing pad, making
it possible to simplify the structure of the polishing pad and to
manufacture the polishing pad with high efficiency. Therefore, the
polishing pad can be directly fixed to a platen of a polishing
device for polishing semiconductor devices, without needing an
elastic layer, such as the elastic backside pad interposed
therebetween. This is because the present polishing pad permits an
accurate surface deformation along the surface of the wafer on the
basis of the elastic deformation of the partitions, whereas the
conventional polishing pad utilizes an elastic backside pad to
cause its surface to be deformed along the surface of the
wafer.
[0039] Preferably, the width of the each groove is arranged within
a range of 0.1-0.3 .mu.m so that the polishing pad can be deformed
along the surface of the wafer with further improved accuracy,
owing to the elastic deformation of the partitions interposed
between adjacent ones of the grooves. More preferably, the depth of
the each grooves is arranged within a range of 0.1-0.4 .mu.m,
thereby improving durability of the polishing pad and minimizing an
amount of change of properties of the polishing pad due to a
dressing process or the like.
[0040] As is understood from the aforementioned description, the
present polishing pad is different from the conventional polishing
pad in the mechanism for ensuring the desired surface deformation
of the polishing pad along with the surface of the wafer. This
distinguishably advantageous structure of the present invention
permits that the polishing pad and the surface of the wafer to be
polished are pressed against with each other with a reduced
pressing force, thereby further facilitating flows of the slurry
interposed between the polishing pad and the surface of the wafer,
and assuring substantially even distribution of the pressing force
over an entire area of the surface of the wafer to be polished.
Accordingly, the polishing pad constructed according to the present
invention permits an excellent polishing and planarization of the
surface of the semiconductor devices with extremely high
accuracy.
[0041] Preferably, the circumferential grooves comprises a
multiplicity of generally concentric annular grooves which are
formed over a sufficiently large area of the front surface of the
polishing pad including a very radially inner portion. Namely, the
radially inner most groove of the polishing pad has the radius of
curvature of 1.0 mm or smaller. This arrangement makes it possible
to effectively increase a region of the polishing pad serving for
polishing, without increasing the diameter of the polishing pad.
This arrangement is also effective to keep pace with recent
tendency of enlargement of wafer, with ease. It should be
appreciated that the use of the turning tool constructed according
to the first aspect of the invention enables to form such an
annular groove having a relatively small radius of curvature.
[0042] It is noted that if the groove width is smaller than 0.005
mm, it becomes difficult to form such a fine groove by turning and
to control the distribution of the slurry desirably. If the groove
width is larger than 1 mm, the polishing pad is likely to be
excessively bent at its grooved portions, resulting in
deterioration of polishing accuracy. Preferably, the groove width
is set within a range of 0.1-1.0 mm. Further, if the generally
concentric grooves are formed with a pitch of smaller than 0.2 mm,
the polishing pad is likely to suffer from a hydroplane phenomenon
depending upon a viscosity of the slurry. If the generally
concentric grooves are formed with a pitch of larger than 2.0 mm,
the polishing pad is less likely to deform accurately along with
the surface of the wafer, resulting in deterioration of polishing
accuracy. The pitch of the grooves may be desirably determined,
taking into account a required polishing accuracy, a kind of
material of interconnects of the semiconductor device, or the like.
Generally, the pitch of the grooves is determined within a range of
1.0-2.0 mm.
[0043] Preferably, the radially outer most one of the grooves has a
radius of curvature of not less than 100 mm.
[0044] Yet preferably, the radially inner most one of the grooves
has a radius of curvature of not larger than 10 mm, and the
polishing pad has a diameter which is made smaller than that of the
working piece. This polishing pad constructed according to this
preferred form is effectively used for polishing a significantly
large sized wafer, e.g., a wafer having a diameter of not smaller
than 200 mm. Since the radially inner useless area of the polishing
pad is effectively minimized, the polishing pad of this preferred
form makes it possible to polish such a large-sized wafer without
increasing a diameter thereof.
[0045] It may be possible to vary the pitch of the grooves in the
radial direction of the polishing pad. For instance, the grooved
portion of the surface of the polishing pad may be divided into
three regions, namely, an inner circumferential region, an
intermediate region, and an outer circumferential region. The pitch
of the grooves may desirably vary among the three regions so that
the polishing pad may polish evenly the surface of the
semiconductor device.
[0046] It may also be possible that the circumferential grooves are
spaced apart from each other in the radial direction of the
polishing pad with a constant pitch. This arrangement facilitates a
manufacture of the polishing pad, and stabilizes a desirable
deformation of the surface of the polishing pad following the
surface of the wafer on the basis of the elastic deformation of the
partitions interposed between adjacent ones of the grooves.
[0047] According to another preferred form of the polishing pad of
the present invention, the base for the polishing pad is made of a
rigid urethane foam and the circumferential grooves are formed with
a width of 0.20-0.30 mm, a depth of 0.1-1.0 mm, more preferably
0.1-0.4 mm and a pitch of 1.0-2.0 mm. In this form of the polishing
pad, kinds of the rigid urethane foam are not particularly limited.
Preferably, the base is formed of a rigid urethane foam having a
density at around 700 kg/m.sup.3 and a tensile strength of 50
kg/cm.sup.3 or more. More preferably, the rigid-urethane foam
includes cells having a diameter at around 0.02 mm at the volume
ratio of 30%. In this respect, a rigid urethane foam used as
packing material, generally has a density at around 100 kg/m.sup.3
and a tensile strength at around 15 kg/cm.sup.3. It should be
appreciated that a solid resin member may also form the base.
[0048] The above-indicated fourth object of the invention may be
achieved according to a fourth aspect of the invention, which
provides a machine equipped with a turning tool constructed
according to the first aspect of the invention and adapted to form
a polishing pad constructed according to a third aspect of the
present invention. The machine for grooving a base for a polishing
pad made of a resin material, comprises (a) a bed; (b) a platen
including a hollow shaft member supported by the bed via bearing so
that the hollow shaft member is rotatably about a C-axis which is
perpendicular to the bed, a suction plate fixed to one of opposite
axial end portion of the hollow shaft member remote from the bed
and formed with a plurality of through holes arranged evenly over
an entire area thereof for attracting the base for the polishing
pad to be placed on the suction plate; (c) drive mechanism for
rotating the platen about the C-axis and for positioning the platen
at a suitable angular position; (e) a gate-shaped column having two
legs which are opposed to each other with a spacing therebetween
and a cross rail extending between and being perpendicular to the
two legs, the gate-shaped column being movable in a direction of
X-axis with the cross rail extending across the platen; (f) at
least one saddle mounted on the cross rail so as to be movable in a
direction of Y-axis extending along with the cross rail; (g) a tool
rest mounted on the saddle so as to be independently reciprocally
movable in a direction of a Z-axis, the tool rest adapted to
detachably hold a fixed tool comprising the turning tool
constructed according to the first aspect of the invention; (h)
drive motors for moving and positioning the platen, the column and
the saddle and the tool rest; and (i) a numerical control apparatus
totally control an operation of the drive motor, wherein the hollow
shaft member of the platen is connectable to an external air
suction device so as to attract the base for the polishing pad on
the suction plate by a suction force applied from said air suction
device to said base for said polishing pad, and wherein the machine
is operable to cut by the turning tool circumferential grooves into
a surface of the base of the polishing pad with the base for the
polishing pad being attracted on the suction plate.
[0049] The machine constructed according to the fourth object of
the present invention, makes it possible to form by turning the
circumferential grooves on the surface of the base for a thin
polishing pad, which is made of a resin material in a solid state
or a foamed state, e.g., a rigid urethane foam, by using a specific
turning tool constructed according to the first aspect of the
present invention. The circumferential grooves can be formed with
high accuracy and high stability over a substantially entire area
of the surface of the base for the polishing pad. Therefore, the
machine is able to effectively form the polishing pad constructed
according to the third aspect of the present invention.
[0050] In this respect, there are known various kinds of
conventional general-purpose turning machines, such as lathes and
machining centers. These known turning machines are provided for
mainly processing a metallic work piece, and are equipped with a
rotative platen adapted to fix the metallic working piece thereon
by holding a periphery of the work piece, a tool rest holding a
cutter (fixed tool), a drive mechanism for positioning the cutter
relative to the working piece and for rotating the cutter and the
work piece relative to each other, and a controller for controlling
operation of the driving mechanism, for example. That is, the known
turning machines may possibly be operable to cut the
circumferential grooves with a desired pitch into a work piece
fixed to the rotative platen. However, since the base for the
polishing pad as the work piece is made of the resin material and
has a relatively small thickness, it is therefore difficult to
stably fix such a special working piece, i.e., the base for the
polishing pad on the platen by only holding the peripheral portion
of the base. For the above reasons, the conventional turning
machine is incapable of controlling a depth of cut of the turning
tool by a slight amount, which is required for cutting the desired
circumferential grooves into the surface of the base for the
polishing pad. Thus, the conventional turning machine is never
utilized for forming the polishing pad constructed according to the
third aspect of the present invention.
[0051] Moreover, the polishing pad to be processed by the machine
of the present invention has a large variety of required
properties, needing a change of the turning tool depending upon
properties of the desired polishing pad. However, the conventional
turning machine suffers from a small degree of freedom in choosing
turning tools, and accordingly is not able to meet such
requirements in the grooving process of the polishing pad.
[0052] In addition, the conventional turning machine has an
excessively large rigidity for processing the base for the
polishing pad, thus making the grooving process complicated and
time-consummative. Namely, in the conventional turning machine,
each of the moving components has a relatively large mass and a
resultant large inertia, making it difficult to ensure a faster
operation of the components of the machine.
[0053] In the grooving machine for producing the polishing pad
according to the present invention, the base for the polishing pad
as the work piece is suctioned on and firmly fixed to the circular
platen. This arrangement eliminates or reduces a possible
distortion of the base generated upon rotating the circular platen.
Further, the circular platen is arranged to substantially evenly
apply the suction force over an entire area of a rear surface of
the base for the polishing pad, making it possible to form by
turning the groves into the surface of the base with improved
processing accuracy and high stability.
[0054] In the grooving machine of the present invention, the
gate-shaped column is disposed on the bed with the circular platen
interposed between its legs, while a saddle is formed on the cross
rail of the gate-shaped column adapted to support tools. This
arrangement ensures a high stable and accurate positioning of the
tools relative to the working pieces in comparison with the case
where the tools are supported by a single arm, while assuring an
increased working area of the tools.
[0055] According to a first preferred form of the machine of the
invention, the machine further comprises: (j) an ion blowing device
for neutralizing the static electricity charged in the polishing
pad and chips, for separating the chips from the fixed tool and the
polishing pad, said ion blowing device including: an ion generating
device for generating ion, an ion extruding nozzle for extruding
the ion toward the cutting part of the fixed tool, an air blowing
device for blowing air together with the ion.
[0056] According to a second preferred form of the machine of the
invention, the tool rest detachably support a rotative tool
consisting of a milling cutter unit and/or a drilling unit. In this
preferred form of the machine of the present invention, the tool
rest is adapted to selectively support a milling cutter unit
including a milling cutter for grooving and a drill unit having a
drilling cutter, as well as the turning tool for grooving
constructed according to the first aspect of the invention.
Therefore, the machine of this preferred form is operable to
execute not only the grooving process but also milling cutting and
drilling processes.
[0057] In one advantageous form of the second preferred form of the
machine of the invention, the milling cutter unit includes at least
one milling cutter fixedly supported by a tool shaft extending
along a center axis thereof, wherein the at least one cutter
includes a disk-shaped body member and a plurality of cutting edges
disposed at an outer peripheral portion of said body member at
regular angular intervals, and each having a wedge angle within a
range of 20-40 degrees, and a front clearance angle within a range
of 30-40 degrees, a tooth width within a range of 0.3-2.0 mm, and a
side cutting edge angle of 0-2 degree. The use of the milling
cutter having a special construction as described above enables the
machine to process the base for the polishing pad with increased
degree of freedom. For instance, the use of this special milling
cutter permits the present machine to form with ease grooves
arranged in a grid pattern, a spiral pattern, a spoke-wise pattern
and other formable patterns.
[0058] Preferably, the machine comprises a plurality of the milling
cutters which are fixedly disposed onto the tool shaft such that
the tool shaft extend through center axes of the plurality of the
milling cutters and the plurality of milling cutters are spaced
apart from each other in an axial direction of the tool shaft with
a uniform pitch of 0.1 mm or more. This arrangement makes it
possible to cut a plurality of grooves into the surface of the base
for the polishing pad, simultaneously.
[0059] In another advantageous form of the second preferred form of
the machine of the invention, the drill unit comprises a
single-spindle type or a multiple-spindle type drill unit, the
drill unit including a drill having a drill diameter of 0.5-1.5 mm,
a drill length of 20-30 mm two cutting edges of helix angle of 1-10
degrees, wherein the drill is a straight drill having no
back-tapered portion at cutting edges thereof and having a shape
edge that has a conical angle with no chisel portion of 55-65
degrees. The use of this drilling unit permits the present machine
to cut holes into or through the base for the polishing pad,
resulting in an increased degree of freedom in processing the base
for the polishing pad. In particular, the drill of the drilling
unit is specifically arranged as described above, in other words,
the drill has the sharp edge in the conical shape so as to
facilitate entrance of the drill into the base, and the cutting
edges arranged at its body portion with a relatively dull helical
angle so as to perform cutting of the base with a slight amount of
feed per revolution. This arrangement minimizes a possibility that
the end of the drill damages the base. Thus, the machine equipped
with the drilling unit can form a hole at a desired diameter with
high accuracy.
[0060] According to a third preferred form of the machine of the
invention, the machine further comprises a sequential control
system adapted to control operation of the drive motor in place of
or in addition to the numerical control apparatus. The use of the
sequential control system may slightly restrict operation speed and
command accuracy in comparison with the numerical control
apparatus. However, the use of the sequential control system may
sometimes be advantageous in terms of cost depending upon kinds of
applications, thus extending a field of application of the present
machine.
[0061] According to a fourth preferred form of the machine of the
invention, the machine includes two of the saddles, wherein at
least one of the tool holders of the two saddles is adapted to
detachably support the fixed tool comprising the turning tool
comprising a cutting part arranged to have a tooth width within a
range of 0.005-1.0 mm, a wedge angle within a range of 15-35
degrees, and a front clearance angle within a range of 65-45
degrees, and an other one of the tool holders of the two saddles is
adapted to detachably support the rotative tool selected from a
group consisting of the milling cutter unit and the drilling unit.
In this arrangement the machine is equipped with both of the
turning tool and the rotative tool with high efficiency, whereby
the machine is able to execute various kinds of processing with
improved operation efficiency.
[0062] According to a fifth preferred form of the machine of the
invention, the machine includes only one of the saddle, wherein the
tool holder of the saddle is adapted to interchangeably support the
fixed tool comprising the turning tool constructed according to the
first aspect of the invention or the rotative tool selected from a
group consisting of the milling cutter unit or the drilling unit.
In this arrangement, the grooving machine is made compact in size
and simple in construction, while enabling selective use of the
fixed tool and the rotative tool.
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] The forgoing and/or other objects features and advantages of
the invention will become more apparent from the following
description of preferred embodiments with reference to the
accompanying drawings, in which like numerals are used to represent
like elements and wherein:
[0064] FIG. 1A is an front elevational view of a grooving machine
constructed according to one preferred embodiment of the present
invention, and FIG. 1B is an plane view of the grooving machine of
FIG. 1A, while FIG. 1C is a side elevational view of the grooving
machine of FIG. 1A;
[0065] FIG. 2 is an elevational view in a vertical or a
longitudinal cross section of the grooving machine of FIG. 1A;
[0066] FIG. 3 is an fragmentally enlarged view of the grooving
machine of FIG. 1A;
[0067] FIG. 4A is a plane view of a platen of the grooving machine
of FIG. 1, and FIG. 4B is a cross sectional view of the platen of
FIG. 4A taken along line B-B of FIG. 4A;
[0068] FIG. 5A is a plane view of a suction plate of the grooving
machine of FIG. 1, FIG. 5B is an axial cross sectional view of the
suction plate, FIG. 5C is a fragmentally enlarged view of the
suction plate, FIG. SD is an enlarged view of a X portion of FIG.
5C, and FIG. 5E is an enlarged cross sectional view taken along
line E-E of FIG. 5D;
[0069] FIGS. 6A and 6B are a front and a side views of the grooving
machine of FIG. 1A, which are depicted for explaining a primary
part of the grooving machine of FIG. 1A;
[0070] FIGS. 7A and 7B are a plane and a rear view of the grooving
machine of FIG. 1A, which are depicted for explaining a primary
part of the grooving machine of FIG. 1A;
[0071] FIGS. 8A and 8B are a front and a cross sectional views of
saddles of the grooving machine of FIG. 1, which are depicted for
explaining a drive system of the saddles movable along a Y1 axis
and a Y2 axis, respectively;
[0072] FIGS. 9A and 9B are a front and a side elevational view of
an inside of the grooving machine of FIG. 1A, which are depicted
for explaining a drive system of the tool holders movable along a
Z1 axis and a Z2 axis, respectively;
[0073] FIG. 10 is a fragmentally side elevational view of the
grooving machine of FIG. 1A, which shows one operating state of the
grooving machine in which a milling tool is attached to the tool
holder;
[0074] FIG. 11 is a view corresponding to FIG. 10, which shows
another operating state of the grooving machine in which a drill
tool is attached to the tool holder;
[0075] FIG. 12 is a view corresponding to FIG. 10, which shows yet
another operating state of the grooving machine in which a fixed
tool is attached to the tool holder;
[0076] FIG. 13 is a block diagram schematically illustrating an
essential structure of a numerical control device employed for
controlling operation of the grooving machine of FIG. 1A;
[0077] FIG. 14 is a block diagram schematically illustrating an
essential structure of a sequence control device employed for
controlling operation of the grooving machine of FIG. 1A;
[0078] FIG. 15A is a front elevational view of an ion blowing
device used in the grooving machine of FIG. 1 for neutralizing
charged components of the grooving machine, and FIGS. 15B and 15C
are a side and a bottom elevational view of the ion blowing device,
respectively;
[0079] FIGS. 16A and 16B are a front and a side views of a turning
tool having a single cutting part, which is usable in the grooving
machine of FIG. 1;
[0080] FIGS. 17A and 17B are a side and a front view of a turning
tool having a plurality of cutting parts, which is usable in the
grooving machine of FIG. 1;
[0081] FIG. 18 is an enlarged front elevational view of one example
of a tool tip;
[0082] FIGS. 19A and 19B are a front and a side view of a tool
holder to which the tool chip of FIG. 18 is attached;
[0083] FIG. 20 is an explanatory view showing one example of
operation state of the grooving machine of FIG. 1, in which a
plurality of tool chips attached to the tool holder are arranged in
one direction;
[0084] FIG. 21 is an explanatory view showing one example of
operation state of the grooving machine of FIG. 1, in which a
plurality of tool chips of FIG. 18 are fixed to the tool
holder;
[0085] FIG. 22A is an enlarged side view of one example of a
multi-edged tool tip in which a plurality of cutting parts are
laminated one another, and FIG. 22B is an enlarged front
elevational view of the multi-edged tool of FIG. 22A;
[0086] FIG. 23A is an enlarged side view of another example of a
multi-edged tool tip in which a plurality of cutting edges are
laminated one another, and FIG. 23B is an enlarged front
elevational view of the tool tip of FIG. 23A;
[0087] FIG. 24A is a side view of one example of a cutting device
usable in the grooving machine of FIG. 1, FIG. 24B is a front
elevational view of the cutting device, and FIG. 24C is a cross
sectional view of the cutting device, taken along line C-C of FIG.
24B;
[0088] FIG. 25A is a plane view of one example of a milling cutter
attachable to the milling tool of FIG. 10, and FIGS. 25B is a
fragmentally enlarged view of the milling cutter of FIG. 25A;
[0089] FIG. 26A is a plane view of one example of a drill attached
to a drill unit of FIG. 11, and FIG. 26B is an exploded view of a
major cutting edge portion of the drill of FIG. 26A;
[0090] FIGS. 27A and 27B show one example of a polishing pad of
foamed urethane having a plurality of generally concentric grooves
formed by cutting process executed by the grooving machine of FIG.
1, wherein FIG. 27A is a fragmentally enlarged plane view of the
polishing pad, and FIG. 27B is a fragmentally enlarged view in
cross section of the polishing pad;
[0091] FIGS. 28A and 28B show another example of polishing pad of
foamed urethane having a plurality of grooves arranged at grid
pattern formed by milling process executed by the grooving machine
of FIG. 1, wherein FIG. 28A is a fragmentally enlarged plane view
of the polishing pad, and FIG. 28B is a fragmentally enlarged view
in cross section of the polishing pad;
[0092] FIG. 29 is yet another example of polishing pad of foamed
urethane having a plurality of grooves arranged in a radial pattern
formed by milling process executed by the grooving machine of FIG.
1;
[0093] FIG. 30 is still another example of polishing pad of foamed
urethane according to examples 1 and 2 by using the grooving
machine of FIG. 1 equipped with the turning tool of FIG. 17;
[0094] FIG. 31 is a fragmentally enlarged view in axial cross
section of the polishing pad of FIG. 30;
[0095] FIG. 32A is a microscopic photographic view of 30 times
magnification and FIG. 32B is a microscopic photographic view of
100 times magnification, which shows a cross sectional shape of
grooves of one example of a polishing pad of the present invention,
which grooves are formed by using the turning tool of the present
invention;
[0096] FIG. 33A is a microscopic photographic view of 30 times
magnification and FIG. 33B is a microscopic photographic view of
100 times magnification, which shows a cross sectional shape of
grooves of a comparative example of a polishing pad;
[0097] FIG. 34 is a microscopic photographic view of 120 times
magnification showing a cross sectional shape of grooves of another
example of a polishing pad of the invention;
[0098] FIG. 35 is a microscopic photographic view of 120 times
magnification showing a cross sectional shape of grooves of another
comparative example of a polishing pad;
[0099] FIG. 36 is a microscopic photographic view showing grooves
formed in a radially inner portion of a polishing pad of the
present invention;
[0100] FIG. 37 is a view schematically showing a static model used
in a simulation of relationship between a groove width variation
and an abutting pressure variation of a polishing pad of the
invention with respect to a wafer;
[0101] FIG. 38 is a graph showing a distribution of an abutting
pressure of the polishing pad on a surface of the wafer of the
static model of FIG. 37; and
[0102] FIG. 39 is a graph showing a relationship between a peak
pressure applied on the surface of the wafer and a rate of
variation or error of a groove width.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0103] Referring first to FIGS. 1A-1C, there is shown a schematic
construction of a grooving machine according to one preferred
embodiment of the present invention. The grooving machine is
equipped with a turning tool for cutting grooves, which is
constructed according to one preferred embodiment of the invention.
The grooving machine is used for producing a polishing pad
according to one preferred embodiment of the invention in
accordance with a method according to one preferred embodiment of
the invention.
[0104] The grooving machine constructed according to the present
embodiment is operable to produce by cutting circumferential
grooves, e.g., a multiplicity of generally concentric annular
grooves in the present embodiment, on a surface of a base for the
polishing pad made of a resin material, e.g., a foamed urethane pad
15. The grooving machine comprises the following components:
[0105] (a) a circular platen 1 rotatable under control about C-axis
extending in a vertical direction as seen in FIG. 1A;
[0106] (b) a gate-shaped column 11 reciprocatory movable under
control in a direction of X-axis;
[0107] (c) two saddles 8A, 8B mounted on a cross rail 7 and
reciprocatory movable along a screw-thread 10 (Y1-axis) and a
screw-thread 14 (Y2-axis);
[0108] (d) two tool holders 18, 19 mounted on the two saddles 8A,
8B; respectively, and reciprocatory movable along a screw-thread
12A (Z1-axis) and a screw-thread 12B (Z2-axis);
[0109] (e) a numerical control device 102 (see FIGS. 13, 14)
adapted to control operation of motor and a control axis;
[0110] (f) an ion blower 114 as an ion blowing device (see FIG. 15)
for neutralizing charged components;
[0111] (g) a fixed tool 69 as a turning tool in the form of a
single cutting edge tool 58 and a multiple cutting edges tool 74
(see FIG. 12) for cutting grooves;
[0112] (h) a cutting device (see FIG. 24); and
[0113] (i) a rotative tool 57 in the form of a milling tool 59 and
a drill unit 65 (see FIGS. 10, 11).
[0114] There will be described in detail a general construction of
the grooving machine and specific construction of the respective
components listed above, with reference to the accompanying
drawings, sequentially.
[0115] FIGS. 1A-1C shows an entire construction of the grooving
machine according to the present embodiment. The circular platen 1
is fixedly mounted on a bed 3 so as to extend parallel to an upper
surface of the bed 3. The circular platen I is rotatable about the
C-axis extending perpendicular to the upper surface of the bed 3,
i.e., extending in the vertical direction as seen in FIG. 1A. The
bed 3 further supports a pair of first guide rails 5A, 5B
horizontally mounted on opposite sides of its upper surface. The
first guide rails 5A, 5B extend parallel to each other in a
longitudinal direction of the bed 3 while being spaced apart from
each other with the circular platen 1 interposed therebetween. The
gate-shaped column 11 is mounted on the first guide rails 5A, 5B so
that the gate-shaped column 11 is movable along the first guide
rails 5A, 5B in the horizontal direction. The gate-shaped column 11
includes a pair of legs in the form of column portions 4A, 4B
mounted on the first guide rails 5A, 5B, respectively, and a cross
rail 7 extending between the column portions 4A, 4B so as to
connect the column portions 4A, 4B to each other. The thus formed
gate-shaped column 11 is driven by a pair of screw shaft 6A (first
X axis) and 6B (second X axis) disposed on the bed 3 so as to
extend along the guide rails 5A, 5B, respectively, in a direction
of an X-axis as indicated by an arrow in FIG. 1B. The pair of screw
shafts 6A, 6B are synchronously rotated by a drive motor 40 which
will be described later with reference to FIG. 7B. The drive of the
gate-shaped column 11 is controlled by a suitable control device
that will be described later. A pair of second guide rails 9A, 9B
are disposed on one of opposite side faces of the cross rail 7 so
as to extend in a direction of a Y-axis as indicated by an arrow in
FIGS. 1A and 1B, which is perpendicular to the X-axis. On the
second guide rails 9A, 9B, the two saddles 8A, 8B are mounted so as
to be movable along the guide rails 9A, 9B, i.e., in the direction
of the Y-axis. The two saddles 8A, 8B are driven by respective
screw shafts 10, 14 disposed on the side face of the cross rail 7
so as to extend along the guide rails 9A, 9B. The screw shafts 10,
14 are rotated by suitably electric drive motors (not shown) under
control of the suitable control device. The two saddles 8A, 8B
support tool rests 18, 19 mounted thereon, respectively, such that
the tool rests 18, 19 are movable in a direction of a Z-axis
extending in the vertical direction as seen in FIG. 1A (as
indicated by an arrow). The tool rests 18, 19 are driven by
respective ball-screws 12A, 12B disposed on the saddles 8A, 8B so
as to extend along the Z-axis. The screw shafts 12A, 12B are
rotated by respective electric motors 13A, 13B so that the tool
rests 18, 19 are moved in the direction of the Z-axis independently
of each other. The gate shaped column 11, the saddles 8A, 8B, and
the tool rests 18, 19 may be formed by desired metallic materials,
preferably rigid light metallic materials such as a hard aluminum
alloy or the like.
[0116] (a) Circular Platen (C-Axis)
[0117] Referring next to FIG. 2, the circular platen 1 and a
housing member of the circular platen 1 are both shown in their
axial cross sections. FIG. 2 also shows a driving mechanism for
rotating the circular platen 1 and an air suction device in the
form of a suction blower 25 installed within the bed 3 so as to
apply a vacuum to an upper surface of the circular platen 1 to
thereby attract the base for a desired polishing pad for the CMP,
in the form of the foamed urethane pad 15, on the upper surface of
the circular platen 1. FIG. 3 shows an enlarged view in axial cross
section of a position holding member 38 adapted to place the
circular platen at its suitable angular position about the C-axis,
which is determined based on the angular position of the circular
platen 1 detected by controlling the rotation of the circular
platen 1 about the C-axis. FIG. 4 shows a plane view and an axial
cross sectional view of the circular platen 1 in which a plurality
of air flow passages are evenly formed therethrough so that the
vacuum delivered from the suction blower 25 is evenly applied to a
rear surface of the foamed urethane pad 15. FIG. 5 shows a suction
plate 16 assembled in the surface of the circular platen 1. The
suction plate 16 has a plurality of tiny air holes 16a formed
therethrough and tiny grooves 16b, 16c connecting the air holes 16a
so that the vacuum is evenly applied to the rear surface of the
foamed urethane pad 15, thus preventing deformation of the surface
of the urethane pad due to stress concentrated at a local portion
of the foamed urethane pad upon cutting grooves on the urethane
pad.
[0118] As is understood from FIGS. 2 and 3, the circular platen 1
is supported by a hollow shaft member in the form of a hollow
center shaft 17 that is disposed in and supported by the bed 3 via
the housing 2, such that the hollow center shaft 17 is rotatable
about a center axis thereof. Described in detail, the center shaft
17 has an outward flange portions 17a integrally formed at an
axially upper end portion thereof. The circular platen 1 is placed
on and fixed to an annular upper surface of the outward flange
portion 17a so as to extend in a radial direction perpendicular to
the center axis of the center shaft 17. The center shaft 17 is
fixed at its axially upper and lower end portions to the housing 2
via upper and lower bearings 33, 34, respectively. The type, size
and level of dimensional accuracy of the upper and lower bearings
33, 34 are suitably determined so that an amount of deflection
occurred at an outer peripheral portion and the upper surface of
the circular platen 1 is significantly reduced. The housing 2 is
fixed to the bed, whereby the center shaft 17 is rotatably
supported by the bed 3.
[0119] The axially lower end portion of the center shaft 17
protrudes axially downwardly from the housing 2. To the protruded
end portion of the center shaft 17, an optional power transmittal
member, e.g., a pulley 22 is fixed. On the other hand, a drive
motor 21 operable for controlling the rotation of the circular
platen 1 about the C-axis is fixed to a sheet portion 3a of the bed
3. The output power of the drive motor 21 is transmitted via
pulleys 22, 23 and a belt 24 rounded about the pulleys 22, 23, thus
generating a rotation of the center shaft 17 and the circular
platen 1 fixed to the center shaft 17 about the C-axis. In this
respect, power transmitting mechanism for transmitting the output
power of the drive motor 21 to the center shaft 17 may otherwise be
constituted by utilizing a combination of gears, or any other
possible power transmittal members.
[0120] The hollow center shaft 17 has a bore 17b serving as an air
passage. The bore 17b is held in fluid-tight communication at its
upper end with a plurality of communication holes la formed through
the central portion of the circular platen 1, and at its lower end
with an air hose 28 of the suction blower 25 via a coupling 27
supported by a support 26 fixed to a seat portion 3b of the bed 3.
In this condition, the vacuum generated in the suction blower 25 is
applicable to the rear surface of the foamed urethane pad placed on
the upper surface of the circular platen 1 through the bore 17b of
the center shaft 17 and the communication holes 1a of the circular
platen 1. Therefore, the vacuum application needed for holding the
foamed urethane pad on the surface of the circular plate 1 can be
executed during the rotation of the center shaft 17. In this
respect, the upper open end of the communication holes 1a are
closed by a suction plate 16 which is placed on the upper surface
of the circular platen 1. As shown in FIG. 5, the suction plate 16
is formed with a plurality of suction holes in the form of air
holes 16a and grooves 16b, so that the vacuum is evenly applied in
the upper surface of the suction plate 16 through the communication
holes 1a and the air holes 16a and the grooves 16b, thus assuring
firmly holding of the foamed urethane pad 15 on the surface of the
suction plate 16. As is understood from the aforementioned
description, the position holding member 38, the drive motor 21 and
the suitable power transmittal members cooperates to form a drive
mechanism adapted to rotate the circular platen 1 and place the
circular platen 1 at a suitable angular position, in the present
embodiment.
[0121] Referring back to FIGS. 2 and 3, a disk plate 30 having a
plurality of projections 31 is fixed to the protruding end portion
of the center shaft 17, while plurality of sensors 32 are fixed to
the lower end face of the housing 2 so as to be located above the
projections 31 with a slight spacing therebetween in the vertical
direction as seen in FIG. 2. The sensors 32 detect the projections
31 to thereby detect the angular position of the circular platen 1.
This mechanism is used for detecting the angular position of the
circular platen 1 rotating about the C-axis under control, and
positioning the circular platen 1 at its desired angular position.
When the grooving machine is operated to form a multiplicity of
small-width straight grooves arranged in a grid pattern on the
surface of the foamed urethane pad 15, by using the milling cutter,
the positions of the sensors 32 and the projections 31 are changed
so that the sensors 32 can detect angular positions of the circular
platen 1 each time the circular platen 1 is rotated by 45 degree
about the C-axis. In the grooving process, the circular platen 1 is
fixed each time the circular platen is rotated by 90 degree about
the C-axis, to thereby cutting the straight grooves on the surface
of the urethane pad in the grid pattern. In the present embodiment,
the position holding member 38 is constituted by a positioning bush
35 having a tapered hole, which is fixed to a predetermined angular
position of the lower surface of the circular platen 1, and a
piston member 37 having a shaft 36 whose upper end portion is
tapered, which is disposed on a corresponding angular position of
the bed 3. The piston member 37 may be of pneumatic type, hydraulic
type or alternatively electromagnetic type. It should be
appreciated that the structure of the position holding member 38 is
not particular limited to the illustrated one. For instance, a
Curvic coupling device (curvic: trademark) may be employed instead
of the tapered shaft 36, for thereby permitting the detection of
the angular position of the circular platen 1 at angular intervals
of not larger than 45 degree.
[0122] FIG. 4A shows a plane view of the circular platen 1, while
the FIG. 4B shows a cross sectional view of the circular platen 1
taken along line B-B of FIG. 4A. A material for producing the
circular platen 1 may be preferably selected from light metals
including aluminum alloy, titanium and the like, thereby lowing a
moment of inertia of the circular platen 1, thus permitting a
prompt startup or stop of the rotation of the circular platen. In
particular, the material of the circular platen 1 is desired to be
less likely to cause the secular change of the circular platen 1,
like strain, to exhibit a heat resistance, and to have sufficient
stiffness and strength. While the communication holes la is formed
through the central portion of the circular platen 1 for
introducing the suction force applied from the suction blower 25
into the upper surface of the circular platen 1 through, the
circular platen 1 is also formed with a plurality of leading
grooves 1c, 1d for leading the suction force into the outer
circumferential portion of the circular platen 1. The circular
platen 1 is further provided with a plurality of generally
concentric grooves 1e, through which the plurality of leading
grooves 1c, 1d extending in the radial directions are held in
communication with each other. A plurality of circumferential walls
If defined between adjacent ones of the annular grooves 1e serve as
supports on which the suction plate 16 is placed.
[0123] Referring next to FIGS. 5A, 5B, 5C, there are shown a plane
view, an axial cross sectional view, and a fragmentally enlarged
view of the suction plate 16. In addition, FIG. 5D shows an
enlarged view of an X part of FIG. 5C, and FIG. 5E shows a cross
sectional view taken along line E-E of FIG. 5D. As shown in FIG.
5E, the suction plate 16 functions to support the foamed urethane
pad 15 to be placed thereon. The suction plate 16 is provided with
the multiplicity of tiny air holes 16a evenly dispersed over the
entire surface of the suction plate 16, so that the foamed urethane
pad 15 is fixed onto the surface of the suction plate 16 by the
suction force evenly applied to the back surface thereof through
the air holes 16a. Like the circular platen 1, the suction plate 16
is made of a material preferably selected from light metals
including hard aluminum alloy, titanium, and the like, and ceramic
materials.
[0124] In the light of flexibility of the foamed urethane pad 15,
specific arrangement is needed for ensuring desired suction
condition of the foamed urethane pad 15 on the suction plate 16.
More specifically described, when the currently processed portion
on the front surface of the foamed urethane pad is remote from
suctioned portions on the rear surface of the foamed urethane pad
15 to which the suctioned force is applied, the processed foamed
urethane pad 15 is prone to be deformed or displaced in the
direction in which the cutting tool is forwarded, possibly causing
deterioration of dimensional accuracy of the formed grooves. To
cope with this problem, the suction plate 16 is required to be
capable of evenly applying the suction force on the rear surface of
the foamed urethane pad 16 placed thereon. Therefore, the air hole
16a are evenly dispersed over the entire area of the suction plate
16 with a substantially regular pitch. Each of the air holes 16a is
dimensioned to have a suitable diameter, taken into account the
thickness of the foamed urethane pad 16, so that the suction force
applied through the air hole 16a to the corresponding portion of
the rear surface of the urethane pad 16 does not cause deformation
of the urethane pad 16. For instance, the air hole 16a is
dimensioned to have a diameter of about 2 mm, when the foamed
urethane pad 15 has a thickness of 1.4 mm. As shown in FIG. 5D,
adjacent ones of the air holes 16a are held in communication with
each other through communication grooves 16b, thus assuring further
improved evenness of the suction force. The suction plate 16 is
further provided with a plurality of annular generally concentric
clearance grooves 16c, which are formed on predetermined radial
portion of the front surface of the suction plate 16. In the case
where the grooving machine is operated to perform a boring process
with a boring unit in the form of a drill unit 65 (which will be
described later with reference to FIGS. 11 and 16) attached
thereto, the suction plate 16 is further provided with a clearance
grooves (not shown) having a diameter slightly larger than the
diameter of a drill of the drill unit 65 and formed through its
predetermined portion.
[0125] (b) Gate-Shaped Column (X-Axis)
[0126] Referring next to FIGS. 6A and 6B, there are shown a plane
view and a side view of the gate-shaped column 11 that is placed on
the first guide rails 5A, 5B, which are disposed on the bed 3 with
the circular platen 1 interposed therebetween. FIGS. 7A and 7B show
drive mechanism for driving the gate-shaped column 11 in the
direction of the X-axis as shown in FIG. 7A. Namely, FIG. 7A is a
plane view of the bed 3 on which the pair of screw shafts 6A, 6B
are disposed so as to extend along with the guide rails 5A, 5B,
respectively. The motions of the screw shafts 6A, 6B in their axial
direction i.e., in the direction of X-axis, are controllable. FIG.
7B shows a power transmitting system for controlling the rotation
of the screw shaft 6A, 6B by using a single belt 43.
[0127] Described more specifically, the gate-shaped column 11
includes the pair of columns 4A, 4B and the cross rail 7 fixed at
its both ends with the columns 4A, 4B, respectively, for thereby
connecting the columns 4A, 4B. The pair of columns 4A, 4B are
placed on the first guide rails 5A, 5B, respectively, so that the
gate-shaped column 11 is movable in the direction of an X axis
along the guide rails 5A, 5B, by the drive force generated by the
screw shafts 6A, 6B. Alternatively, the gate-shaped column 11 may
be formed as an integral form by welding or casting.
[0128] As shown in FIGS. 7A, 7B, the first pair of screw shaft 6A,
6B are disposed on the opposite side portions of the upper surface
of the bed 3, so as to extend in the direction of the X-axis
parallel to each other. A pair of ball nuts 39A, 39B are
thread-engaged with the screw shafts 6A, 6B, respectively. To the
ball nuts 39A, 39B, the columns 4A, 4B are fixed, respectively,
whereby the gate-shaped column 11 is moved in the direction of the
X-axis according to the axial motion of the ball nuts 39A, 39B
along the screw shafts 6A, 6B. A drive motor 40 is disposed within
the bed 3. The drive motor 40 has an output shaft equipped with a
pulley 41. The rotation of the pulley 41 is transmitted to a pair
of pulleys 42A, 42B, fixed to the respective screw shafts 6A, 6B,
via a belt 43 wound around the pulleys 41, 42A, 42B, so that
rotations of the pulleys 42A, 42B are synchronized with each other,
thus moving the ball nut 39A, 39B simultaneously. The drive
mechanism for driving the screw shafts 6A, 6B is not particularly
limited to the illustrated one. For instance, the screw shafts 6A,
6B may be driven by respective drive motors directly connected
thereto, which motors are controlled to provide synchronized
operation with each other.
[0129] (c) Two Saddles 8A, 8B Mounted on a Cross Rail (Y1-Axis,
Y2-Axis)
[0130] Referring back to FIG. 6A, there is shown a front view of
two saddles 8A, 8B. Two saddles 8A, 8B are mounted on the second
guide rails 9A, 9B disposed on the cross rail 7 so as to extend
over the two symmetrical columns 4A, 4B in the direction of Y-axis
perpendicular to the Z-axis and the X-axis, as shown by arrows in
FIGS. 6A and 6B. Therefore, the two saddle systems 8A, 8B are
movable in the direction of Y-axis along the second guide rails 9A,
9B. The two saddle systems 8A, 8B are driven by respective drive
motors whose operation is controllable so as to place the saddles
8A, 8B at respective desired positions. FIG. 8A is a view
corresponding to that of FIG. 6A, in which the two saddles 8A, 8B
are removed from the second guide rails 9A, 9B. As is apparent from
FIG. 8A, ball-screw shafts 10, 14 are disposed on the cross rail 7
so as to extend along with the second guide rails 9A, 9B, i.e., in
the Y-axis direction. The screw shaft 10 is driven by an Y1-axis
control motor 47, while the ball-screw shaft 14 is driven by an
Y2-axis control motor 48. FIG. 8B shows power transmittal members
constituting the motors 47, 48.
[0131] As is apparent from FIGS. 8A and 8B, the second guide rails
9A, 9B are disposed on the front side surface 7a of the cross rail
7 so as to extend parallel to each other. Each of the saddles 8A,
8B has four linear bearings 49 fixed on the rear surface thereof.
The saddles 8A, 8B are mounted on the second guide rails 9A, 9B at
their linear bearings, so that the saddles 8A, 8B are slidably
movable along the second guide rails 9A, 9B in the Y-axis
direction. Further, the ball-screw shafts 10, 14 are also disposed
on the front side surface 7a of the cross rail 7 so as to extend
parallel to the second guide rails 9A. 9B, which are driven by the
motor 47 (Y1-axis) and the motor 48 (Y2-axis) to make a rotational
motion. This rotational motion of the screw shafts 10, 14 are
converted into longitudinal motions of nuts 50, 51 along the screw
shafts 10, 14, respectively, which nuts 50, 51 are thread-engaged
with the screw shafts 10, 14 and firmly fixed to the rear surfaces
of the saddles 8A, 8B. Therefore, the saddles 8A, 8B are
reciprocally moved in the Y-axis direction in accordance with the
longitudinal motion of the nuts 50, 51 caused by the rotation of
the screw shafts 10, 14. The motor 47 for rotating the screw shaft
10 is operable under control by a suitable control device so that
the longitudinal motion of the nut 50, i.e., the displacement of
the saddles 8A in the Y1-axis is suitably controlled. Likewise, the
motor 48 for rotating the drive shaft 14 is operable under control
by a suitable control device so that the longitudinal motion of the
nut 51, i.e., the displacement of the saddles 8B in the Y2-axis is
suitably controlled. In this respect, the saddles 8A, 8B share the
same guide rails 9A, 9B, so that the motors 47, 48 are suitably
controlled to prevent interference between the saddles 8A and 8B in
the Y-axis direction.
[0132] The tool rests 18, 19 disposed on the saddles 8A, 8B may
hold different kinds of cutting tools, for example. In this case,
the saddles 8A, 8B are selectively driven. While the two saddles
8A, 8B are disposed on the same side, i.e., the front side of the
cross rail 7 and utilize the same second rails 9A, 9B for their
displacement in the Y-axis direction, the structure of the two
saddles 8A, 8B are not partially limited, but may otherwise be
modified or changed. For instance, the second guide rails 9A, 9B
may be provided for each of the two saddles 8A, 8B. The saddles 8A,
8B may be disposed on the opposite sides, i.e., the front and rear
sides of the cross rail 7, respectively, rather than the same side
of the cross rail 7. In the case where the tool units attached to
the tool rests 18, 19 may interfere with the other components or
devices installed on the bed 3, it is effective to change
arrangement of the saddles 8A, 8B on the gate-shaped column 11,
thus avoiding or eliminating the undesirable interfere of the tool
units and the other components.
[0133] (d) Tool Rests Disposed on the Two Saddles (Z1 Axis, Z2
Axis)
[0134] FIG. 6A shows the tool rests 18, 19 mounted on the saddles
8A, 8B on the front side of the cross rail 7. FIGS. 9A, 9B show a
front elevational view and a side elevational view of tool-rest
support mechanism in which the tool rest 19 are indicated by a
two-dot chain line. Further, FIG. 10 shows one example of the
operating state of the tool rest 19 in which a milling cutter unit
59 as a rotative tool 57 is fixed to the tool rest 1 9. FIG. 11
shows another example of the operating state of the tool rest 19 in
which a drill 82 as the rotative tool 57 is fixed to the tool rest
19. FIG. 12 shows yet another example of the operating state of the
tool rest 19 in which a single edged tool 58 or a multi-edged tool
74 as a fixed tool 69 is fixed to the tool rest 19. It should be
noted that both of the tool rests 18, 19 may be provided with
various kinds of rotative tools and fixed tools in a possible
variety of combinations. The tool rests 18, 19 may also be provided
with the cutting device 77 which will be described later or various
kinds of groove cutting tools. For instance, the tool rests 18, 19
may be provided with the rotative tool 57 and the fixed tool 69,
respectively. The tool rests 18, 19 may otherwise be provided with
different fixed tools, e.g., the single edged tool 58 and the multi
edged tool 74, respectively. Alternatively, the tool rests 18, 19
may be provided with different rotative tools 57, namely, the tool
rest 18 is provided with one of the milling cutter unit 59 and the
drill unit 65, while the tool rest 19 is provided with the
other.
[0135] As is apparent from FIG. 9A, a pair of third guide rails 52B
are disposed on the front surface of the saddle 8B so as to extend
in the Z-axis direction, while being parallel to each other. The
tool rest 19 (indicated by the two-dot-chain line) is mounted on
the third guide rails 52B via the four linear bearings 53B, whereby
the tool rest 19 is movable along the third guide rails 52B in the
Z-axis direction. A screw shaft 12B is also disposed on the front
surface of the saddle 8B so as to extend in the Z-axis direction. A
ball nut 55B is threaded engaged with the screw shaft 12B. On the
upper end portion of the saddle 8B, there is disposed a motor 13B
for driving the screw shaft 12B. The operation of the motor 13B is
suitably controlled so as to regulate a feed per revolution (i.e.,
an amount of depth of cut) of a tool fixed to the tool rest 19. A
pair of balancers 56B are also disposed on the upper end portion of
the saddle 8B. The presence of the balancers 56B ensures a stable
weight balance of the tool rest 19 in the Z-axis direction, thus
ensuring smooth displacement of the tool rest 19 and accurate
positioning control of the tool rest 19. As is understood from the
foregoing description, the circular platen 1, the gate-shaped
column 11, the saddles 8A, 8B and the tool rests 18, 19 are driven
and positioned by suitably controlled operation of the motor 21 for
the C-axis control, the motor 40 for the X-axis control, the motors
47, 48 for the Y1-axis and Y2-axis control, and the motor 13A, 13B
for the Z1-axis and Z1-axis control, in the present embodiment.
These drive motors 21, 40, 47, 48, 13A, 13B may be servomotors of a
pneumatic type, a hydraulic type, an electromagnetic type or other
possible types.
[0136] In the present embodiment, the gate-shaped column 11 is
guided to move in the X-axis direction by the first guide rails 5A,
5B, and the saddles 8A, 8B are guided to move in the Y-axis
direction by the second guide rails 9A, 9B, while the tool rests
18, 19 are guided to move in the z-axial direction by the third
guide rails 52A, 52B, as described above. Therefore, the cutting
edges of the tools fixed to the tool rests 1 8, 19 can be
accurately positioned in the above-indicated X, Y and Z-axis
directions by utilizing a numerical control device (hereinafter
referred to as "NC" device) 102. Namely, the NC device controls the
operations of the drive motors 21, 40, 47, 48, 13A, 13B so that the
positions of the gate-shaped column 11, the saddles 8A, 8B and the
tool rests 18, 19 are accurately controlled. Further, the milling
cutter unit 59 and the drill unit 65 are selectively detachably
fixed to the tool rest 19. FIG. 10 shows one operation state of the
grooving machine 10 in which the rotative tool 57 consisting of the
milling cutter unit 59 having a milling cutter 81 (see FIG. 25) is
fixed to the tool rest 19. FIG. 1I shows another operation state of
the grooving machine 10 in which drill unit 65 having a drill 82
(see FIG. 26) is fixed to the tool rest 19.
[0137] There will be described a manner of operation of the
grooving machine of the present invention when the grooving machine
is operated under control of the NC device 102 for producing the
polishing pad multiplicity of straight grooves arranged in the grid
pattern, by way of example. First, the milling cutter units 59 are
fixed to the tool rest 18(19). Subsequently, the motor 21 is
operated under control of the NC device 102 for detecting the
current angular position of the circular platen 1 and then fixing
the circular platen 1 in a predetermined angular position. The
motor 40 is also operated under control of the NC device 102 for
driving the gate-shaped column 11 to a desired position in the
X-axial direction, while the motor 47, 48 are operated under
control of the NC device 102 for driving the saddles 8A, 8B in the
Y-axial direction, while the motors 13A, 13B are operated under
control of the NC device 102 for driving the tool rests 18, 19 to a
desired position in the Z-axial direction. Thus, the milling
cutting unit 59 is accurately positioned on a desired portion of
the foamed urethane pad, which portion is to be processed. With the
milling groove cutting unit 59 being positioned as described above,
the grooving process is performed according to a suitable
processing program stored in a storage device of the NC device 102.
Namely, a desired amount of depth of cut of the milling cutter 81
in the Z-axial direction are provided by the operation of the motor
13A, 13B under control of the NC device 102, while a desired amount
of displacement of feed per revolution of the saddles 8A, 8B in the
Y-axial direction are provided by the operation of the motors 47,
48 under control of the NC device 102.
[0138] On the other hand, in the case where the grooving machine is
operated under control of the NC device 102 for forming a through
hole through the foamed urethane pad 15, the drill unit 65 are
fixed to the tool rest 18 (19). Like the above case where the
grooving machine is operate to cut the grid-patterned grooves into
the surface of the foamed urethane pad 15, the circular platen 1 is
placed in the initial position, while the drill unit 65 is
positioned on a portion of the urethane pad 15 which portion is to
be processed. According to a predetermined processing program
stored in the storage device of the NC device 102, the amount of
depth of cut of the drill unit 65 in the Z-axial direction is
produced by the operation of the motors 13A, 13B under control of
the NC device 102. The rotation speed of the rotative tool 57 is
suitably regulated by controlling the speed of the motor by the NC
device 102.
[0139] When the grooving machine is operated under control of the
NC device 102 for producing a polishing pad having a multiplicity
of generally concentric annular grooves, the fixed tool 69
comprises a selective one of the single edged tool 58 and the
multi-edged tool 74 is fixed to the tool rest 18 or 19 (e.g., the
tool rest 19 as shown in FIG. 12). In this respect, any one of the
single edged tool 58 and the multi edged tool 74 may be selected in
the light of processing condition, a required cost of manufacture,
or the like. The NC device 102 controls displacements of the
gate-shaped column 11 in the X-axis direction, the saddle 8B in the
Y-axis direction, and the tool rest 19 in the Z-axis direction, so
as to place the fixed tool 69 in its initial position.
Subsequently, the circular platen 1 is rotated about the C-axis
under control of the NC device according to the predetermined
control program. The fixing tool 69 is displaced in the Z-axis
direction by a predetermined feed per revolution. In order to
process all grooves at a generally constant process speed, the
rotating speed of the circular platen 1 is changed depending upon
the position of the fixing tool 69 in the Y-axis direction.
[0140] While one of the tool rest 19 has been described in detail
in the aforementioned description, it should be appreciated that
the other tool rest 18 is substantially similar in construction to
the tool rest 19. Thus, the same reference numerals as used with
respect to elements of the tool rest 19 will be used to identify
the elements which are the same as or similar to those in the tool
rest 18, and no redundant description of elements will be provided,
for the sake of simplification of the description. The grooving
machine constructed according to the present embodiment, permits
that the rotative tool 57 (e.g., milling cutter 81 or drill 82) is
fixed to one of the tool rests 18, 19 and the fixed tool 69 (e.g.,
the single edged tool 58 and the multi-edged tool 74) is fixed to
the other one of the tool rests 18, 19. Preferably, these tool
units or other various kinds of tool units are easily detachably
fixed to the tool rests 18, 19, thus facilitating interchange of
the tools. This makes it possible to select and use a suitable tool
depending upon a kind of material of the foamed urethane pad 15,
and condition of the cutting, thus assuring a further improved
dimensional or shape accuracy of the formed grooves. It should be
understood that the motors 21, 40, 47, 48, 13A, 13B may be
constituted by linear motors rather than the illustrated
servomotors, for ensuring an high accuracy of positioning and an
improved speed of response of the circular platen 1, the
gate-shaped column 11, the saddles 8A, 8B, the tool rests 18, 19
which are moved by these motors in the X, Y1, Y2, Z1, Z2 axes.
[0141] (e) Numerical Control Device to Control Motor and Control
Axis
[0142] Numerical control device 102 is adapted to control operation
of the motors 13A, 13B, 21, 40, 47, 48, so that the circular platen
1, the gate-shaped column 11, the saddle 8A, 8B, the tool rests 18,
19 are accurately and smoothly positioned in the C, X, Y and X
axes, respectively. The numerical control device 102 permits to
control the motors 13A, 13B to regulate the feed per revolution of
the tool rests 18, 19 at minute units. The numerical control device
102 enables an automatic synchronizing control operation of the
plurality of motors, according to a suitable control program that
is stored in its storage device in advance. In this storage device
of the NC device 102, a plurality of grooving patterns to be
reproduced on the surface of the foamed urethane pad 15 are stored
in advance. A suitable grooving pattern is selected from the stored
grooving patterns, then the operations of the processing program
for the selected grooving patterns with respect to the respective
control axes C, X, Y, Z are prepared. According to this
predetermined processing program, the grooving machine of this
embodiment is automatically operated so as to reproduce the
selected grooving pattern on the surface of the polishing pat.
[0143] Referring next to FIG. 13, there is shown a block diagram
schematically showing a control system of the NC device 102 adapted
to control operation of the grooving machine. Described in detail,
the NC device 102 includes data input section 101, a central
processing unit (CUP) 103, a data storage section 104 and an I/O
interface. Upon starting the grooving process under control of the
NC device 102, a tool command representing a kind of required tool,
and dimensional information of the required tool is applied to the
numerical control device 102 through the data input section 101.
The required tool is suitably determined depending upon a desired
groove pattern, e.g., a grid pattern or a generally concentric
annular groove pattern. This tool command is stored in the data
storage section 104 via the CPU 103. Once an operation command is
applied from the input section 101, the CPU 103 controls operation
of the respective motors 13A, 13B, 21, 40, 47, 48, and the cutting
device 77 according to a suitable processing program with reference
to data stored in the storage section 104, so that the operations
of the circular platen 1, the gate-shaped column 11, the saddles
8A, 8B, the tool rests 18, 19 and the milling cutter unit 59, the
drill unit 65 are accurately controlled. Each motor is equipped
with an encoder. An amount of rotation of the motor detected by the
encoder is applied to the NC device so that the NC device controls
the operation of the grooving machine in a feedback control
fashion. The CPU 103 also controls operation of the suction blower
25, the position holding member 38 of the circular platen 1, the
ion blower 114, and a chip collection device 115.
[0144] It should be appreciated that the operation of the grooving
machine may be controllable by utilizing a sequential control
device 110, instead of the NC device 102 as described above. The
use of the sequential control device 110 instead of the numerical
control device 102 enables to simplify the entire control system
and reduce the cost of the device, although accuracy of control in
positioning, feeding, and cutting are somewhat limited in
comparison with that in the numerical control device. 102.
Therefore, one of the numerical control device 102 and the
sequential control device 110 may be optionally selected depending
upon the use or processability of the foamed urethane pad 15.
[0145] Referring next to FIG. 14, there is shown a block diagram
schematically showing a sequential control system of the sequential
control device 110 adapted to control operation of the grooving
machine. Described in detail, the sequencer device 110 includes an
operation panel 121, a sequencer circuit section 122, a sequential
action determining section 123, and a sequencer data output section
124. Upon starting the grooving process of the grooving machine
under control of the sequencer device 110, various kinds of data
including positional data of the control axes and process data with
respect to feed per revolution, an amount of depth of cut, or the
like, and a suitable sequential control program representing a
predetermined sequence of processing steps, are applied to the
sequencer circuit 122 via the operation panel 121. The sequencer
circuit 122 outputs the data received from the operation panel 121
to the sequential action determining section 123 that comprises a
sequencer unit and relay circuits. The sequential action
determining section 123 outputs action data to the sequencer data
output section 124. The sequencer data output section outputs an
action command signal based on the action data to a positioning
drive motor 125 operable for controlling positions feed rates, and
or depths of cuts of the components arranged in the X, Y,1 Y2, Z1,
Z2 C axes, a drive motor 126 adapted to drive the rotative tool 69,
and a drive motor 127 adapted to drive the cutting device 77, so
that these drive motors 125, 126, 127 are operated according to the
received action command signals. The sequencer data output section
124 is operable to generate next action command signals to the
drive motors 125, 126, 127 each time the operations of these motors
125, 126, 127 according to the current command signals are
terminated. That is, the sequencer device 110 controls the
operation of these drive motors 125 126, 127 in an open-loop
control fashion. In the present embodiment, the positioning motors
125, the drive motors 126, 127 may be constituted by utilizing
pulse motors. Meanwhile, the grooving machine is provided with
various kinds of associated equipments 128 including the ion
blowing device 114, the suction blower 25, the position holding
device 38, the chip collection device 115. The operation of the
associated equipments 128 can be controlled directly through the
operation panel 121.
[0146] (f) Ion Blowing Device
[0147] Referring next to FIGS. 15A, 15B, there is shown the
ion-blowing device 114 adapted to generate and blow positive ions
formed by corona discharge. The ion-blowing device 114 includes a
compressed air generator (not shown) and a blower nozzle 76, so
that the generated positive ions are discharged through the blower
nozzle 76 together with the compressed air. Alternatively, the
positive ions are discharged through a through holes 71(a) 72(a)
which will be described later. This ion-blowing device 114 is
disposed in a portion of the grooving machine such that a protruded
open-end portion of the blower nozzle 76 is located in the vicinity
of the attached cutting tool, e.g., the fixed tool 69 or the
rotative tool 57 (the multi-edged tool 74 is attached in FIGS.
15A-15C by way of example). When the foamed urethane pad 15 is
subjected to the grooving process, chips of the foamed urethane pad
15 are likely to be electrically charged due to friction between
the cutting tools and the urethane pad 15, and stick to the surface
of the urethane pad 15 and the cutting tools, resulting in
difficulty in removing the charged chips from the surfaces of the
cutting tool and the urethane pad. To cope with this problem, the
ion blowing device 114 is operated to blow the positive ions on the
chips stick to the cutting tool and the foamed urethane pad 15,
during the grooving process is executed for the foamed urethane pad
15, whereby the chips are effectively neutralized and removed from
the cutting tool and the urethane pad 15. When the multi-edged tool
74 of the fixed tool is used for forming simultaneously a plurality
of grooves on the foamed urethane pad 15, in which a plurality of
cutting edges are juxtaposed to each other, it is required to
evenly blow the positive ions on the respective cutting edges so
that the positive ions forcedly come into collision with the
charged chips. To meet this requirement, the protruded open-end
portion of the nozzle 76 may be suitably arranged.
[0148] FIGS. 15A-15C show a front, a side and a bottom elevational
view of the ion-blowing device 114 that is fixed to a tool holder
71. The tool holder 71 has a rectangular block shape and detachably
fixed to the side face of the tool rest 18 (19) by means of
suitable fastening means such as a bolt. The tool holder 71 has the
above mentioned through hole 71a formed therethrough in the
vertical direction as seen in FIG. 15A through which positive ions
are discharged. To the bottom face of the tool holder 71, a
rectangular block shaped tool cartridge is fixed such that the tool
cartridge 72 is supported by tapered bush 73 so as to be positioned
in the vertical direction as seen in FIG. 15A. The tool cartridge
72 has the above-indicated plurality of straight holes 72a
extending therethrough in the vertical direction as seen in FIG.
15A. These straight holes 72a are held in communication with the
through hole 71a of the tool holder 71, so that the lower end of
the through holes 71a is exposed to the atmosphere through the
straight holes 72a.
[0149] As shown in FIG. 15A, the multi edged tool 74 is fixed to
the tool holder 71 by way of example. The multi edged tool 74 may
be a tool detachably installable on the tool holder 71 with high
accuracy. For instance, the multi edged tool 74 is fixed to the
tool cartridge 72. The cartridge 72 is positioned relative to the
tool holder 71 by means of tapered bushes 73, 73. The cartridge 72
is guided by the side walls of the tool holder 71, and is firmly
fitted to the tool holder 71 by means of a pressing plate 75 that
is bolted to the tool holder 71. The positive ions can be
discharged from the side of the attached tool through the nozzle
76. In the case where the multi edged tool 74 is attached to the
tool holder 71 as described above with the compressed air, the ion
blowing device 114 may be arranged to blow the positive ion through
the through hole 71a formed through the tool holder 71 and the
straight holes 72a formed through the cartridge 72 instead of or in
addition to the nozzle 76. In the ion-blowing device 114, the
compressed air generator may be disposed within the nozzle 76, or
the straight holes 72a, for example. Alternatively, the compressed
air generator may be constituted by utilizing an external
compressed air source that is held in fluid communication with the
nozzle 76 or the like via an air conduit. It should be appreciated
that the compressed air generator is interpreted to mean the
overall structure thereof including the air conduit connecting
between the external compressed air source and the nozzle 76 or the
like.
[0150] Instead of the multi-edged tool 74, the single edged tool
58, and the rotative tool such as the milling cutter unit 59 and
the drill unit 65 may be mounted on the tool holder 71, likewise.
In this case, the blowout of the ion may be possibly executed
through the nozzle 76. It should be understood that the
construction of the blower passage of the ion blow device 114 is
not limited to the above, but may otherwise be modified, as
needed.
[0151] (g) Fixed Tool (Turning Tool/Cutting Tool)
[0152] (1) Turning Tool (Single Edged Tool and Multi Edged
Tool)
[0153] FIGS. 16A and 16B show a front and a side elevational view
of the single edged tool 58 as one example of the fixed tool 69.
FIGS. 17A-17C shows a bottom, a front and a side elevational view
of the multi edged tool 74 as another example of the fixed turning
tool 69. The single edge tool 58 and the multi edged tool 74 are
suitably used for the grooving process in which the plurality of
generally concentric annular grooves are formed on the surface of
the foamed urethane pad 15.
[0154] The single edged tool 58 has a cutting part 58a that is
arranged as follows so that the single edged tool 58 is suitable
for cutting a working piece made of a resin material, e.g., a
foamed urethane pad. Namely, the cutting part 58a of the single
edged tool 58 has a tooth width: W1 within a range of 0.005-1.0 mm,
a side clearance angle: .theta.1 within a range of 0-2 degrees, as
shown in FIG. 16A. Further, the cutting tooth of the single edged
tool 58 has a wedge angle: .theta.2 within a range of 30-35
degrees, a rake angle: .theta.3 within a range of 10-20, and a
front clearance angle .theta.4 within a range of 45-55 degrees, as
shown in FIG. 16B. These angles of respective parts of the cutting
part 58a of the single edged part 58a are determined taking into
account a problem of interface between the cutting part 58a and
walls of the foamed grooves and a required strength of the cutting
part 58a. Preferably, the single edged part 58a is made of a rigid
material, such as hard metal, high speed steel, carbon steel,
ceramics, cermet, and diamonds.
[0155] As shown in FIGS. 17A-17C, the multi-edged tool 74 has a
thin rectangular plate-like shape and includes a plurality of
cutting parts 58a integrally formed on and protruding from its
bottom end as seen in FIG. 17A, such that the plurality of cutting
parts 58a are arranged in a longitudinal direction of the
multi-edged tool 74 at regular intervals within a range of 0.2-2.0
mm, over a substantially entire area of the bottom end of the
multi-edged tool 74. It is noted that each of the plurality of
cutting parts 58a of the multi-edged tool 74 is dimensioned
identically with the cutting part 58a of the single edged tool 58.
That is, the multi-edged tool 74 serves as a tool tip having a
plurality of cutting parts 58a integrally formed in the end portion
thereof.
[0156] Referring next to FIGS. 18 and 19, there is shown by way of
example the multi-edged tool 74 in the form of the tool tip, which
is fixed to the bottom end portion of the tool holder 71, such that
the multi-edged tool 74 is gripped by and between the tool holder
71 and the pressing plate 75. Positioning pins 73 fitted to the
multi-edged tool 74 is used for positioning the multi-edged tool 74
relative to the tool holder 71. The tool holder 71 equipped with
the multi-edged tool 74 as shown in FIG. 19, may be solely fixed to
the tool holder 18 (19). Alternatively, a plurality of tool holders
71 each equipped with the multi-edged tool 74 may be fixed to the
tool holder 18(19), as shown FIG. 20. In this case, the cutting
parts 58a of the plurality of multi-edged tools 74 may be arranged
at regular intervals, thus permitting high efficiency in cutting a
plurality of grooves on the foamed urethane pad 15. As is apparent
from FIG. 21, it may be possible to fixed a plurality of
multi-edged tools 74 to the tool holder 71 such that the cutting
parts 58a are arranged at regular intervals. This arrangement
facilitates the formation of the plurality of grooves on the foamed
urethane pad 15, likewise.
[0157] Referring next to FIGS. 22, 23, there are schematically
shown another type of multi-edged tools 92, 95 according to the
present invention by way of example. As is apparent from FIG. 22,
the multi-edged tool 92 includes a plurality of cutting tips 90
each having a single cutting part 58a. The plurality of cutting
tips 90 are superposed on each other and are detachably fixed
together and fixed to the lower end portion of the tool holder 71
by means of bolts 91 such that the cutting tips 90 are spaced apart
from each other with regular intervals in the width direction of
the tool holder 71. As is apparent from FIG. 23, the multi-edged
tool 95 includes a plurality of cutting tips 93 each having a
single cutting part 58a. Unlike the multi-edged tool 92, the
cutting tooth tips 93 are superposed on each other with spacers 94
interposed between adjacent ones of the cutting tooth tips 93. The
presence of the spacers 94 makes it easy to keep the spacing
between adjacent ones of the cutting tooth chips 93 constant. The
lamination consists of the plurality of cutting tooth tips 93 and
the spacers 94 interposed between adjacent ones of the cutting tips
93 are detachably fixed together and fixed to the lower end portion
of the tool holder 71 by means of bolts 91. The thus constructed
multi-edged tools 92, 95 permit an effective muss-production of the
tools, an improved flexibility for a change of the pitch and an
ease replacement of the cutting parts 58.
[0158] (2) Cutting Tool
[0159] Referring next to FIGS. 24A-24C, there are respectively
shown a side elevational view, a front elevational view and a cross
sectional view taken along line C-C of FIG. 24B of the cutting
device 77 which is adapted to be mounted on the tool rest 18 (19)
disposed on the saddle 8A (8B) of the cutting machine constructed
according to the present embodiment. The cutting device 77 is
operable to cut primary peripheral portion of the foamed urethane
pad 15 to shape the external form of the foamed urethane pad 15
desirably. More specifically described, the cutting device 77
includes: a base 78; a fourth guide rails 63A, 63B disposed on the
base 78 so as to extend parallel to each other in the Z-axis
direction; a tool rest 64 disposed on the base 78 via the pair of
fourth guide rails 63A. 63B so as to be movable in the Z-axis
direction; a cutting tool holder 66 mounted on the tool rest 64;
and a power source 62 disposed on the base 78 so as to generate a
drive power by which the tool rest 64 is moved in the Z-axis
direction. A cutting tool 61 is fixed to the cutting tool holder 66
such that a base portion of the cutting tool 61 is fitted into a
cutting tool base 83 formed in the cutting tool holder 66, while
being supported by the a pair of tool supports 65 with its
protruding end portion supported by a stopper pin 80. An output
member of the power source 62 is connected to a support member 67
disposed on the tool rest 64 via a connecting metal member 68, thus
transmitting output power of the power source 62 to the tool rest
64. Thus, the cutting tool 61 is driven in the Z-axis direction. It
should be understood that the power source 62 may comprises a
piston-cylinder mechanism of pneumatics type or hydraulic type, or
a solenoid-type actuator. It should be further understood that the
cutting tool 61 may otherwise be constituted by a suitable turning
tool for assuring further improved cutting ability of the cutting
device 77.
[0160] (h) Rotative Tool (Milling Cutter and Drill)
[0161] (1) Milling Cutter
[0162] FIG. 25A shows a front view of one example of a milling
cutter 81 for forming a fine groove, which is fixed to the grooving
milling cutter unit 59. FIG. 25B shows an enlarged view of cutting
parts 79 of the milling cutter 81 of FIG. 25A. The milling cutter
81 is a thin circular disk member, which has a center hole 81a
formed therethrough and a plurality of cutting part 79 integrally
formed in its outer peripheral portion such that the plurality of
cutting part 79 are arranged in a circumferential direction of the
grooving milling cutter 81 with a uniform pitch. Each of the
cutting parts 79 is dimensioned to have a wedge angle: .theta.5
within a range of 20-45 degrees, since the wedge angle: .theta.5
smaller than 20 degrees may cause undesirable shortening of the
life of the grooving milling cutter 81, while the wedge angle:
.theta.5 larger than 45 degrees may cause deterioration of cutting
capability of the cutting tooth 79. Further, the each cutting parts
79 is dimensioned to have a rake angle: .theta.6 within a range of
30-40 degrees, more preferably at around 30 degrees, since the rake
angle: .theta.6 smaller than 30 degrees may cause deteriorated
stability of the milling cutter 81, while the rake angle: .theta.6
larger than 40 degrees may cause deterioration of cutting
capability of the cutting tooth 79. Yet further, the each cutting
tooth 79 is dimensioned to have a side cutting edge angle within a
range of 0-2 degrees and a tooth width within a range of 0.3 mm-2.0
mm. The thus formed milling cutter 81 is disposed radially
outwardly on a tool shaft formed on the lower portion of the
grooving milling cutter unit 59 and rotated in a predetermined
circumferential direction by the drive motor 126. The number of the
milling cutter 81 fixed to the tool shaft is not particularly
limited. For instance, a plurality of grooving milling cutters 81
may be fixed to the tool shaft with constant intervals within a
range of 0.1 mm or more, so that a plurality of grooves arranged in
a grid pattern are formed on the foamed urethane pad 15 with
improved efficiency.
[0163] (2) Drill
[0164] FIG. 26A shows a front elevational view of one example of a
drill 82 to be fixed to the drill unit 65, and FIG. 26B shows an
exploded view of a cutting part 82a of the drill 82. As shown in
FIG. 26A, the drill 82 has a diameter: D1 within a range of 0.5
mm-1.5 mm and a length: L1 within a range of 20-30 mm. As shown in
FIG. 26B, the cutting part 82a of the drill 81 includes two cutting
edges 83, 83. The end edge portion of the drill 82 has a cone angle
.theta.8 within a range of 55-65 degrees, more preferably at around
60 degrees, thus assuring a smooth inserting of the drill 81 into
the work piece. A helix angle: .theta.7 of the two cutting edges
83, 83 is arranged to be held within a range of 1-10 degrees,
preferably at about 5 degrees. This arrangement makes it possible
to gradually cut a part of the foamed urethane pad 15 located
around the edge of the drill 82, thereby forming a desired hole
having a predetermined diameter. The number of the drill 82 fixed
to the drill unit 65 is not particularly limited. For instance, a
plurality of drill 82 may be fixed to the drill unit 65 to form a
multi-shaft type drill unit, so that a plurality of holes are
formed into the foamed urethane pad 15 with improved
efficiency.
[0165] There will be described a method of producing a multiplicity
of grooves on the surface of the foamed urethane pad 15 by using
the grooving machine constructed according to the present invention
by way of example.
[0166] (i) Concentric Fine Grooves
[0167] Referring next to FIGS. 27A, 27B, there is shown a polishing
pad fabricated according to one preferred embodiment of the
invention by way of example. The polishing pad is formed by cutting
a multiplicity of generally concentric grooves into the surface of
the foamed urethane pad 15 having a thickness:T1 within a range of
1.0 mm-2.0 mm. The generally concentric grooves have a width: W1
within a range of 0.005-1.0 mm, a depth: D1 within a range of
0.2-2.0 mm, and a pitch: L2 within a range of 0.2-2.0 mm. For
producing the polishing pad of the present invention, initially,
the single-edged cutting tool 58 or the multi-edged cutting tool 74
is fixed to the tool rest 18(19), while a base for desired
polishing pad, e.g., the foamed urethane pad 15 is placed on the
suction plate 16 of the circular platen 1. Preferably, the foamed
urethane pad 15 is shaped to have a circular-disk shape identical
in size with the circular platen 1 in advance, by cutting. The
cutting of the foamed urethane pad 15 may be executed by means of
cutting device 77 fixed to the tool rest 18 (19). In the case where
the foamed urethane pad 15 has a diameter smaller than the suction
plate 16, an annular covering member may be placed on the outer
peripheral portion of the suction plate 16 located radially outward
of the foamed urethane pad 16, so that the air holes 16a open in
the outer peripheral portion of the suction plate 16 is effectively
closed by the annular covering member. The suction plate 16 may be
modified so that only a portion of the suction plate 16 serving for
suctioning the urethane pad 15 is provided with the air holes 16a.
Alternatively, the communication grooves 16b formed in the suction
plate 16 may be partially closed so that distribution of the
suction force on the suction plate 16 is divided into local
sections.
[0168] With the base for the foamed urethane pad 15 placed on the
circular platen 1 as described above, the suction blower 25 is
operated, whereby the base for the foamed urethane pad 15 is firmly
fixed on the circular platen 1 by the suction force applied on the
rear surface thereof. A predetermined revolution speed of the
circular platen 1 about the C-axis during the grooving operation is
set in advance to a suitable control device such as the NC device
102 and the sequential control device 110 so that every groove is
cut at the same turning speed. The gate-shaped column 11, the
saddle 8A (8B) and the tool rest 18 (19) are moved to be placed in
their initial positions in the X-axis, Y-axis and Z-axis
directions, respectively, under control of the suitable control
device. In addition, radial positions of the respective generally
concentric annular grooves are determined in the Y-axis direction
depending upon the number of grooves cut into the surface of the
foamed urethane pad 15 according to control program of the control
device. A predetermined amount of displacement of the tool rest 18
in the Z-axis direction is set to the control device in advance so
as to control an amount of depth of cut of the single edged tool
58. Thus, the cutting device is on standby. Upon starting cutting,
the rotation of the circular plate 1 about the C-axis is started at
the predetermined revolution speed. The cutting by tool 58 is
started at the predetermined amount of depth of cut. Namely, the
tool 58 executes a predetermined number of cuttings by the slight
amount of depth of the cut, thereby cutting one fine annular groove
into the surface of the base for the foamed urethane pad 15.
[0169] The tool rest 18 and the saddle 8A is subsequently displaced
in the Y-axis direction so as to subsequently form the multiplicity
of grooves. When the formed urethane pad has a relatively large
area and a great number of grooves are required to be formed, the
multi-edged tool 74 is preferably employed. The multi-edged tool 74
may consist of 10-30 single-edged tools juxtaposed to each other,
for example. The use of the multi-edged tool 74 makes it possible
to form a great number of grooves with high efficiency.
[0170] Meanwhile, the cutting of the grooves into the formed
urethane pad 15 causes a problem of chips. Namely, the kind or
shape of the cutting chip may vary depending upon materials of the
base of the polishing pad pieces. For instance, the chips may be a
powder form or a ribbon form. In particular, the cutting chip is
likely to be electrically charged, and accordingly to be adhered to
the urethane pad 15, the cutting tool, e.g., the single edged tool
58 or the like. This makes it difficult to assure a complete
removal of the cutting chip by only executing air blowing. To cope
with this problem, the grooving machine of the present embodiment
is equipped with the ion blower. The ion blower is operated to
discharge positive ions, which are charged enough to neutralize the
chips, through the nozzle open in the vicinity of the cutting part
of the tool 58, thus neutralizing the electrically charged chips by
the positive ions, resulting in an desired removal of the cutting
chips from the urethane pad 15 and the single-edged tool 58.
Preferably, a nozzle of a suitable vacuum system is disposed in the
vicinity of a cutting portion of the urethane pad so as to vacuum
the cutting chips from the cutting portion, to thereby prevent
undesirable disperse of the cutting chips. This arrangement is
effective to execute the grooving process with high accuracy. The
synchronization of the motions of the single cutting tool 58 in the
Z-axis direction, the saddle 8A (8B) in the Y1 (Y2)-axis direction
and the circular platen 1 about the C-axis enables to form a swirl
groove on the foamed urethane pad 15. After the grooving process is
terminated, the cutting device 71 may be usable to cut the circular
urethane pad 15.
[0171] (j) Grid Patterned Fine Grooves
[0172] Referring next to FIG. 28, there is shown one example of a
polishing pad having a plurality of grooves arranged in the grid
pattern. This polishing pad is formed by cutting a multiplicity of
straight grooves arranged in the grid pattern into the base for the
polishing pad, e.g., the foamed urethane pad 15 having a thickness
of 1.4 mm. Each of the straight grooves has a width of 0.8 mm, a
depth of 0.5 mm and a pitch of 6.35 mm. For producing this grid
grooved polishing pad, initially, the rotative tool unit 57
equipped with the milling cutter 81 is fixed to the tool rest 19
disposed on the saddle 8B, while the urethane pad 15 as a working
piece is placed on the circular platen 1. Subsequently, the angular
position of the circular platen 1 about the C-axis is detected, and
then the circular platen 1 is held in its initial angular position,
under control of suitable control device, e.g., the NC device 102
or the sequencer 110. For forming the grooves in the grid pattern,
the circular platen 1 placed in its initial angular position is
then rotated about the X-axis by 90 degrees to be held in its first
processing angular position. The gate-shaped column 11, the saddle
8B and the tool rest 19 are moved to be placed in their initial
positions in the X-axis, Y-axis and Z-axis directions,
respectively, under control of the control device. A predetermined
pitch of displacement of the gate-shaped column in the X-axis in
the grid pattern is set in advance, thus eliminating a need for a
surplus displacement of the tool rest 19 in the Y-axis
direction.
[0173] With the circular platen 1 being held in its first
processing angular position, and with the tool rest 19 held in its
initial position, the process for cutting the grid-patterned
grooves is initiated. The gate-shaped column 11 is subsequently
moved in the X-axis direction by the predetermined pitch of
displacement corresponding to the pitch of the grid-patterned
grooves, each time one straight groove is formed, whereby a
multiplicity of straight grooves extending parallel to each other
are formed on the urethane pad 15. After a desired number of
straight grooves is formed on the surface of the foamed urethane
pad 15 positioned in the first processing angular position of the
circular platen 1, the circular platen 1 is then rotated about the
C-axis by 90 degrees so as to be placed and held in its second
processing angular position. Then, a predetermined number of
grooves are formed on the surface of the urethane pad 15 so as to
extend parallel to each other and cross the previously formed
grooves at right angles. Thus, the desired grid grooves polishing
pad is obtained. Upon cutting the grooves on the foamed urethane
pad 15 by using the milling cutter 81, the chips in the form of
powder are produced and dispersed around the cutting part of the
urethane pad 15 and are likely to be adhere to the urethane pad 15
and the milling cutter 81. Therefore, the above-described
ion-blowing device 114 should be employed.
[0174] (k) Radial Grooves
[0175] The grooving machine constructed according to the present
invention may form radially arranged grooves on the base for the
polishing pad, e.g., the foamed urethane pad 15. Described more
specifically, the circular platen 1 on which the foamed urethane
pad 15 as the work piece is fixedly placed, is held in a processing
angular position, and then the milling cutter 81 fixed to the tool
rest 19 is moved by a predetermined amount in the Y-axis direction
so as to form a single straight groove extending in a radial
direction of the urethane pad 15. After the single radial groove is
formed, the circular platen 1 is rotated by a predetermined angle
so as to be held in a next processing angular position thereof. The
grooving milling cutter 81 is moved again by the predetermined
amount in the Y-axis direction so as to form another single
straight grooves extending in a radial direction of the urethane
pad 15. The above described reciprocating motion of the grooving
milling cutter 81 in the Y-axis direction and the rotation of the
circular platen 1 about the C-axis are repeated until a desired
number of grooves are formed on the urethane pad 15. Thus, the
polishing pad having the radial grooves is obtained. In this case,
the use of the ion blower is preferable.
[0176] The above described radial grooves may be formed on the
foamed urethane pad 15 which has a multiplicity of generally
concentric annular grooves. Further the above-described radial
grooves may be modified so as to form a polishing pad 200
constructed according to another embodiment of the invention, as
shown in FIG. 29. The polishing pad 200 has curved radial grooves
202. To form this polishing pad, an known endmill (not shown) is
fixed to the drill unit 65. The circular platen 1 is controlled to
be rotated about the C-axis at a predetermined revolution speed and
by a predetermined amount of angle, while being synchronized with
the feed of the tool rest 19 in the Y-axis direction. Thus, the
desired polishing pad 200 having curved radial grooves 202 is
obtained.
[0177] (m) Drilling
[0178] The obtained polishing pads as described above, may be
subjected to a drilling process as needed. The drilling process
makes it possible to form a plurality of fine holes through the
polishing pads. The drilling process may be performed on a working
piece that is not subjected to any grooving process. In order to
perform the drilling process, a special drill 82 is fixed to the
drill unit 65 mounted on the tool rest 19, initially, Subsequently,
the circular platen 1 is positioned about the C-axis, and the
gate-shaped column 11, the saddle 8B and the tool rest 19 are
respectively positioned in the X-axis, Y-axis and Z-axis
directions. Then, the tool rest 19 is moved downwardly in the
Z-axis direction by a predetermined amount of feed, assuring a
predetermined amount of depth of cut of the drill 82. Thus, a
desired hole is formed through the grooved urethane pad or the work
piece.
[0179] The grooving machine may be operated under control of the
suitable control device to form automatically the plurality of
holes on the base for the polishing pad on the basis of coordinate
values in the X, Y, and Z axes each representing a portion of the
hole to be formed on the surface of the base for the polishing pad,
which are stored in the memory of the control device in advance.
Since the end of the drill 82 has a conical shape and has no
cutting edge, the drill 81 is initially compresses the base for the
polishing pad by the conical shaped edge, and then gradually cut
the compressed part of the polishing pad by the cutting edge 58a
formed in a body portion of the drill 81, whereby the drill 81 is
able to be smoothly inserted into the inside of the base for the
polishing pad. Thus, the drill 82 is able to form a desired hole
even when the base for the polishing pad is made of a soft
material, such as a foamed urethane. In the light of the fact that
the working piece for forming the polishing pad has a relatively
small thickness, the suction plate 16 may be formed with recesses
at portions corresponding to the portions of the base for the
polishing pad in which the holes is formed by drilling. The
diameter of the recess is made larger than the diameter of the
drill 81. This arrangement makes it possible to effectively guide
the conical shaped edge of the drill 81, and to facilitate forming
the through holes by drilling on the base for the polishing pad
such as the foamed urethane pad. In the drilling process, the use
of the ion blower is preferable for facilitating removal of the
chips.
[0180] While the presently preferred embodiments of this invention
has been described above by reference to the accompanying drawings,
for illustrative purpose only, it is to be understood that the
present invention is not limited to the details of the illustrated
embodiments, but may be otherwise embodied.
[0181] For instance, single edged tool may be arrange to have a
cutting part which is curved arcuately in its width direction. The
opposite end portions of the curved cutting part may be protrude
outward of an intermediate portions interposed between the opposite
end portions in the width direction. The single edged tool may be
otherwise arranged to have a tip portion being serrated, namely to
have a saw-toothed cutting part. The side surfaces of the cutting
part may be serrated, as needed.
[0182] While the grid patterned grooves are formed on the surface
of the base for the polishing pad by using a milling cutter 81 in
the grooving machine of the illustrated embodiment, the grid
patterned grooves may be formed more efficiently by utilizing a
single edged tool or a multi edged tool that is fixed to the tool
rest 18 (19) that is reciprocally movable in the Y-axis direction
at a relatively high speed, e.g., 50-180 m per minute. More
specifically described, the grooving machine is modified such that
the saddles 8A, 8B are reciprocally moved in the Y-axis direction
by means of linear motors disposed so as to extend along the guide
rails 9A, 9B, in stead of the ball-screw shafts 10, 14. The use of
the linear motors enables the above-indicated high-speed reciprocal
motion of the saddles 8A, 8B and the tool rest 18, 19 in the Y-axis
direction, in comparison with the ball-screw shafts 10, 14 which
permits the reciprocal movement of the saddles 8A, 8B at 10 m per
minute at most. Thus, the modified grooving machine, which has the
linear motors as a drive power source of the saddles 8A, 8B in the
Y-axis direction, is capable of cutting the grid patterned grooves
into the base for the polishing pad with significantly improved
efficiency. In addition, the modified grooving machine utilizes the
single or multi edged tool rather than the milling cutter 81. This
arrangement is effective to prevent undesirable melt of the base of
the polishing pad due to heat caused by frictional contact of the
milling cutter 81 with the base for the polishing pad, depending
upon kinds of materials of the base for the polishing pad.
[0183] It is also to be understood that the present invention may
be embodied with various other changes, modification and
improvements, which may occur to those skilled in the art, without
departing from the spirit and scope of the invention defined in the
following claims.
EXAMPLES
[0184] To further illustrate the present invention, there will be
described some examples of the invention. It is to be understood
that the invention is not limited to the details of these examples,
but may be embodied with various changes, modifications and
improvements, which may occur to those skilled in the art, without
departing from the spirit and scope of the invention defined in the
appended claims.
[0185] There were prepared two specimens of the polishing pad
according to Examples I and 2 of the present invention as shown in
FIGS. 30, 31 by cutting multiplicity of generally concentric
annular grooves 130 into surfaces of respective foamed urethane
pads 15 by using respective multi-edged tools 74 each constructed
according to the present invention as indicated in the following
Table 1. Described in detail, each of the specimens of Examples 1
and 2 is formed by using the grooving machine of the present
invention. The foamed urethane pad 15 attracted on the suction
plate 16 of the circular platen 1 is rotated about the C-axis at a
speed of 150 revolutions per minute, and the multi-edged tool 74
fixed to the tool rest 18 is cut into the foamed urethane pad 15 at
a feed per revolution of 0.01 mm/rev. The prepared specimens of the
polishing pad of the Examples 1 and 2 had grooves 130 whose
dimension were held within a range of the invention, as indicated
in Table 1.
[0186] On the other hand, specimens of the polishing pads
constructed according to comparative examples 1 and 2 were prepared
by using an optional multi-edged tool having a plurality of cutting
parts whose shape does not meet the requirements of the present
invention as indicated in Table 1. Each specimens of the polishing
pad of the comparative examples 1 and 2 were formed in the same
processing condition as described above with respect to the
specimens of the Examples 1 and 2. Dimensions of the grooves 130 of
the obtained specimens of the comparative examples 1 and 2 were
also indicated in Table 1.
[0187] Microscopic photographic view of cross sections of the
obtained specimens were obtained and evaluate qualities of the
grooves 130 of the obtained specimens in terms of occurrence of
burrs, occurrence of dulled edge of the grooves, and occurrence of
raised portions on the surface of the pad. The results were also
indicated in Table 1. It is noted that the evaluated grooves have
radius of curvatures at around 50 mm. In this respect, FIG. 32A
shows a microscopic photographic view of 30 times magnification and
FIG. 32B is a microscopic photographic view of 100 times
magnification in axial cross section of the groove formed on the
polishing pad of the Example 1. On the other hand, FIGS. 33A, 33B
correspond to the FIGS. 32A, 32B, in which the groove formed on the
polishing pad of the comparative example 1 is shown in its axial
cross section. FIG. 34 is a microscopic photographic view of 60
times magnification showing a cross sectional shape of a groove of
the Example 2 of a polishing pad of the invention; and FIG. 35 is a
microscopic photographic view of 120 times magnification showing a
cross sectional shape of a groove of the comparative example 2 of a
polishing pad.
1 TABLE 1 Comparative Comparative Example 1 Example 2 Example 1
Example 2 Tool Shape Tooth Width 0.35 0.15 0.35 0.15 (mm) Wedge
angle 35.degree. 35.degree. 60.degree. 60.degree. Front 45.degree.
45.degree. 20.degree. 20.degree. Clearance Angle Groove Shape
Groove 0.3 0.1 0.3 0.1 Width (mm) Groove 0.5 0.3 0.4 0.4 Depth (mm)
Groove 2.0 0.5 1.1 1.0 Pitch (mm) Groove Condition Burrs None
Almost Occurred Occurred none Dulled None None -- -- Edges Raised
None Almost Occurred Occurred Portions none Quality Good/Bad Good
Good Bad Bad
[0188] As is understood from Table 1, the polishing pads of the
Examples 1 and 2 which were formed by using the multi edged tool 47
having cutting parts whose dimensions are held within a range of
the invention, have a desired shape and never suffer from the
problem of occurrence of burrs, dulled edges and raised portions.
Therefore, the specimens of the polishing pads according to
Examples I and 2 are capable of establishing a desired distribution
of a slurry, and exhibiting a desired polishing effect. Further,
the grooves 130 of the specimens of the polishing pads of Examples
1 and 2 were formed with high dimensional accuracy, thus
eliminating or minimizing the conventionally experienced problem of
variation in width of the grooves 130 after execution of the
dressing process of the polishing pad. Further, the specimens of
the polishing pads of Examples 1 and 2, have accurately dimensioned
grooves at radially inner portions thereof as shown in FIG. 36. In
FIG. 36, the grooves have radius of curvatures within at around 10
mm. Therefore, the specimens of the polishing pads of Examples 1
and 2 is able to minimize radially inner useless areas thereof.
[0189] On the other hand, the polishing pads of the comparative
examples 1 and 2, which were formed by using the multi-edged tool
having the cutting parts whose dimensions were not held within the
range of the invention, suffer from occurrence of burrs and dulled
edges. Therefore, the specimen of the polishing pad of the
comparative examples 1 and 2 are incapable of exhibiting a desired
polishing effect with stability, and are likely to suffer from
variation in the width of the grooves after execution of the
dressing process of the polishing pad.
[0190] To further clarify technical advantages of the present
invention, a relationship between variation in a groove width and a
variation of an abutting pressure of a polishing pad with respect
to a work, i.e., a wafer, were obtained by conducting a simulation
using a static model as shown in FIG. 37. Where a groove width: "a"
varies among four values: 0.2 mm, 0.2375 mm, 0.2625 mm and 0.3 mm
while a groove pitch is made constant, a variation of the abutting
pressure of the polishing pad applied on a surface of the wafer
were calculated according to the finite element method. The
obtained result as shown in graphs of FIGS. 38 and 39.
[0191] As is understood from the graph of FIG. 38, the abutting
pressure of the polishing pad applied on the surface of the wafer
is significantly increased at open-end edge portions of each
groove. Namely, a significantly high peak pressure is generated at
the open-end edge portions of the each groove. As is also
understood from the graph of FIG. 39, the peak pressure varies over
1.0 gf/mm.sup.2 or more under the condition of a groove width
variation or error of .+-.20%. In the case where the each groove
has a relatively small width selected from a predetermined groove
width range of 0.005-1.0 mm of the present invention, the groove
width error of .+-.20% means a dimensional difference within a
range of 0.002-0.40 mm. This clearly shows that a high dimensional
accuracy of the grooves is significantly important to assure a
desired polishing ability of the polishing pad with high stability.
It should be appreciated that conventional technique for grooving
the polishing pad is absolutely insufficient to form such a fine
multiplicity of circumferential grooves on the base for the
polishing pad with high dimensional accuracy. The aforementioned
high dimensional accuracy of the grooving technique of the present
invention should be appreciated as a prominence effect of the
present invention, which is distinguishable from the conventional
grooving techniques.
* * * * *