U.S. patent application number 10/011315 was filed with the patent office on 2003-05-15 for apparatus and method of conditioning polishing pads of chemical-mechanical polishing system.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Park, Ju-Young, Yoon, Jeong-Goo.
Application Number | 20030092357 10/011315 |
Document ID | / |
Family ID | 19715949 |
Filed Date | 2003-05-15 |
United States Patent
Application |
20030092357 |
Kind Code |
A1 |
Yoon, Jeong-Goo ; et
al. |
May 15, 2003 |
APPARATUS AND METHOD OF CONDITIONING POLISHING PADS OF
CHEMICAL-MECHANICAL POLISHING SYSTEM
Abstract
An apparatus and method for conditioning the polishing pads of a
chemical-mechanical polishing system is disclosed. The conditioning
apparatus includes a tool having a cutting tip and positioned
almost perpendicular to the surface of the polishing pad arranged
on a rotary surface table of the system. The apparatus also has a
horizontal moving unit for moving the tool in a direction almost
parallel to the surface of the polishing pad, a base unit
positioned at a side of the rotary surface table and supporting the
horizontal moving unit, and a vertical moving unit for adjusting a
vertical position of the tool relative to the surface of the
polishing pad. The conditioning apparatus and method of this
invention precisely determines a target depth of cut in a polishing
pad by moving the tool in a vertical direction, thus allowing the
tool to precisely flatten the surface of the polishing pad during a
conditioning process. The apparatus and method also quickly and
uniformly flattens the entire surface of a polishing pad by moving
the tool on the pad in a direction parallel to the surface of the
pad by a radius of the pad or longer distance during a rotation of
the pad.
Inventors: |
Yoon, Jeong-Goo; (Suwon,
KR) ; Park, Ju-Young; (Suwon, KR) |
Correspondence
Address: |
LOWE HAUPTMAN GILMAN & BERNER LLP
Suite 310
1700 Diagonal Road
Alexandria
VA
22314
US
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
|
Family ID: |
19715949 |
Appl. No.: |
10/011315 |
Filed: |
December 11, 2001 |
Current U.S.
Class: |
451/2 |
Current CPC
Class: |
B24B 53/017
20130101 |
Class at
Publication: |
451/2 |
International
Class: |
B24C 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 13, 2001 |
KR |
2001-70572 |
Claims
What is claimed is:
1. An apparatus for conditioning a polishing pad of a
chemical-mechanical polishing system, comprising: a tool having a
cutting tip and positioned almost perpendicular to a surface of the
polishing pad arranged on a rotary surface table of the system; a
horizontal moving unit for moving the tool in a direction almost
parallel to the surface of the polishing pad; a base unit
positioned at a side of the rotary surface table and supporting the
horizontal moving unit; and a vertical moving unit for adjusting a
vertical position of the tool relative to the surface of the
polishing pad.
2. The apparatus according to claim 1, further comprising an
inclination control unit for adjusting an angle of inclination of
the horizontal moving unit relative to the surface of the polishing
pad.
3. The apparatus according to claim 1 or 2, wherein said horizontal
moving unit comprises: a horizontal slide arm holding the tool at a
first end thereof; a horizontal casing connected to a second end of
the horizontal slide arm and having a guide rail for guiding a
horizontal movement of the slide arm relative to the horizontal
casing; and a drive unit for moving the slide arm along the guide
rail of the horizontal casing.
4. The apparatus according to claim 3, wherein said vertical moving
unit comprises a first level screw provided at the first end of the
horizontal slide arm for adjusting the vertical position of the
tool relative to the surface of the polishing pad.
5. The apparatus according to claim 3, wherein the inclination
control unit comprises: a second level screw provided at the base
unit for moving one end of the horizontal casing in a vertical
direction; and a hinge joint connecting a predetermined portion of
the horizontal casing to the base unit and adjusting the angle of
inclination of the horizontal casing relative to the surface of the
polishing pad in response to an operation of the second level
screw.
6. The apparatus according to claim 1, wherein said cutting tip of
the tool is a diamond tip.
7. A method of conditioning a polishing pad of a
chemical-mechanical polishing system, comprising the steps of:
positioning a tool with a cutting tip on an inside or outside
surface of the polishing pad; moving the tool in a vertical
direction so as to align the cutting tip with a target depth of cut
in the pad, thus allowing the cutting tip to flatten the surface of
the pad; rotating the pad around a center of the pad at a constant
velocity; and moving the tool on the pad in a direction parallel to
the surface of the pad by a radius of the pad or longer distance
during a rotation of the pad.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates, in general, to an apparatus
and method of conditioning polishing pads and, more particularly,
to an apparatus and method of conditioning the polishing pads of a
chemical-mechanical polishing system.
[0003] 2. Description of the Prior Art
[0004] In a process of producing semiconductor devices, such as
CMOS, an etchback process or chemical-mechanical polishing process
has been typically used for flattening the surfaces of wafers to a
desired level. Of the above-mentioned two processes, the
chemical-mechanical polishing process (hereinbelow, referred to
simply as "CMP process") has been more preferably used since it
more precisely flattens the surfaces of wafers and gives desired
flatness to the wafers.
[0005] The CMP process performs a mechanical polishing using a
polishing pad and a chemical polishing using polishing slurry at
the same time. During such a CMP process, the polishing pad is
gradually and partially abraded as time goes by, so the pad fails
to desirably polish the surface of a wafer or accomplish desired
flatness of the wafer's surface. In such a case, it is almost
impossible to accomplish intrawafer regional flatness or interwafer
flatness, which are the final aim of the CMP process.
[0006] It is thus necessary to rework such partially abraded
polishing pads, and the reworking of the polishing pads is
so-called a "conditioning" in the field, and has been typically
performed by a pad conditioner.
[0007] FIGS. 1a and 1b are views showing a conventional disc-type
diamond conditioner and a method of conditioning a polishing pad
using the diamond conditioner.
[0008] As shown in FIG. 1a, the conventional disc-type diamond
conditioner 10 comprises a disc body 2 made of stainless steel,
with diamonds 6 having a diameter of several ten micrometers and
fixed to the lower surface of the disc body 2 using a nickel or
chrome plating layer 4. The diamond conditioner 10 is placed on a
polishing pad 14 seated on a rotary surface table 12, and is
rotated by a drive unit 16, thus grinding the surface of the
polishing pad 14 to a desired depth by the diamonds 6. The
polishing pad 14 is thus reworked such that it has a desired
flatness.
[0009] Such a conditioning process must be periodically performed
during a CMP process such that the surface of a polishing pad
maintains a desired flatness of not higher than 2 .mu.m.
[0010] However, the conventional conditioning process using such a
diamond conditioner is problematic in that it has a low
conditioning efficiency due to frictional point contact of the
diamonds with the surface of the polishing pad and uneven cutting
angles of the diamonds. In order to overcome such a problem, the
diamond conditioner is pressed onto the surface of the polishing
pad under high pressure. However, the polishing pad is typically
made of a synthetic polyurethane material, and so the conditioning
process may be not smoothly performed when the conditioner even
slightly excessively compresses the polishing pad. It is also
almost impossible to give a desired flatness of not higher than 2
.mu.m to the surface of the polishing pad.
[0011] In addition, the nickel or chrome plating layer 4 fixing the
diamonds 6 to the lower surface of the conditioner 10 is also
ground during the pad conditioning process, and so the diamonds 6
may be popped-out from the conditioner 10 and undesirably driven
into the polishing pad 14.
[0012] The diamonds, driven into the polishing pad, scratch the
wafer's surface during a CMP process, thus reducing the quality of
wafers. Therefore, such polishing pads, into which diamonds are
driven, must be replaced with new pads, and the conditioner from
which diamonds are popped-out must be replaced with a new one. This
increases the processing cost of a CMP process, including a pad
conditioning process.
[0013] Therefore, it is necessary to provide an apparatus and
method of conditioning such polishing pads, which gives a desired
flatness to the pads without allowing the pads to form scratches on
the surfaces of wafers due to popping-out of diamonds during a CMP
process.
SUMMARY OF THE INVENTION
[0014] Accordingly, the present invention has been made keeping in
mind the above problems occurring in the prior art, and an object
of the present invention is to provide an apparatus and method of
conditioning the polishing pads of a CMP system, which positions a
tool having a cutting tip at a side of a polishing pad such that
the cutting tip is aligned with a target depth of cut in the pad,
and which moves the tool on the pad in a radial direction of the
pad at a constant velocity while rotating the pad, thus
conditioning the pad.
[0015] In order to accomplish the above objects, the present
invention provides an apparatus for conditioning the polishing pads
of a CMP system, comprising: a tool having a cutting tip and
positioned almost perpendicular to the surface of a polishing pad
arranged on the rotary surface table of the system, a horizontal
moving unit for moving the tool in a direction almost parallel to
the surface of the polishing pad, a base unit positioned at a side
of the rotary surface table and supporting the horizontal moving
unit, and a vertical moving unit for adjusting a vertical position
of the tool relative to the surface of the polishing pad.
[0016] The apparatus of this invention preferably further comprises
an inclination control unit for adjusting an angle of inclination
of the horizontal moving unit relative to the surface of the
polishing pad, thus allowing the tool to move horizontally in a
direction precisely parallel to the pad's surface.
[0017] In the preferred embodiment of this invention, the
horizontal moving unit comprises a horizontal slide arm holding the
tool at a first end thereof, a horizontal casing connected to a
second end of the horizontal slide arm and having a guide rail for
guiding a horizontal movement of the slide arm relative to the
horizontal casing, and a drive unit for moving the slide arm along
the guide rail of the horizontal casing. In such a case, the
vertical moving unit preferably comprises a first level screw
provided at the first end of the horizontal slide arm for adjusting
the vertical position of the tool relative to the surface of the
polishing pad.
[0018] In the preferred embodiment, the inclination control unit
comprises a second level screw provided at the base unit for moving
one end of the horizontal casing in a vertical direction, and a
hinge joint connecting a predetermined portion of the horizontal
casing to the base unit and adjusting the angle of inclination of
the horizontal casing relative to the surface of the polishing pad
in response to an operation of the second level screw.
[0019] In the present invention, a diamond tip is preferably used
as the cutting tip of the tool.
[0020] The present invention also provides a method of conditioning
the polishing pads of a CMP system, comprising the steps of
positioning a tool with a cutting tip on an inside or outside
surface of a polishing pad, moving the tool in a vertical direction
so as to align the cutting tip with a target depth of cut in the
pad, thus allowing the cutting tip to flatten the surface of the
pad, rotating the pad around its center at a constant velocity, and
moving the tool on the pad in a direction parallel to the surface
of the pad by a radius of the pad or longer distance during a
rotation of the pad.
[0021] Different from a conventional conditioning apparatus
flattening the surface of a polishing pad through a grinding
process with surface to surface contact between the pad and a
disc-type diamond conditioner, the conditioning apparatus of this
invention conditions the surface of a polishing pad by moving a
tool with a cutting tip on the pad's surface while rotating the pad
after positioning the tool on the pad's surface such that the
cutting tip is aligned with a target depth of cut in the pad.
[0022] That is, during a rotation of the polishing pad on the
rotary surface table of the CMP system, the tool having the cutting
tip is horizontally moved on the pad's surface in a direction from
the edge to the center or from the center to the edge, thus
uniformly flattening the entire surface of the polishing pad while
overcoming the problem of the conventional disc-type diamond
conditioner causing inferior flatness of the pad's surface due to
both uneven distribution of vertical pressures and a difference in
rotating force between the inside and outside portions of the
diamond conditioner.
[0023] In the apparatus and method of the present invention, a tool
having a cutting tip is used during a conditioning process. This
tool gives a desired flatness to the polishing pads without
allowing the pads to form scratches on the surfaces of wafers due
to popping-out of diamonds during a CMP process, different from a
conventional disc-type diamond conditioner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The above and other objects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0025] FIG. 1a is a sectional view of a conventional disc-type
diamond conditioner used for conditioning a polishing pad in the
prior art;
[0026] FIG. 1b is a view showing a method of conditioning a
polishing pad using the diamond conditioner of FIG. 1;
[0027] FIG. 2 is a polishing pad conditioning apparatus in
accordance with the preferred embodiment of the present invention;
and
[0028] FIGS. 3a and 3b are side views of tools used in the
conditioning apparatus of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0029] Reference now should be made to the drawings, in which the
same reference numerals are used throughout the different drawings
to designate the same or similar components.
[0030] FIG. 2 is a polishing pad conditioning apparatus in
accordance with the preferred embodiment of the present invention.
As shown in the drawing, the conditioning apparatus 50 of this
invention is included in a CMP system, and is installed at a side
of a rotary surface table 22 on which a plurality of polishing pads
24 are arranged.
[0031] The conditioning apparatus 50 comprises a tool 26, a
horizontal moving unit, a base unit 42, and a vertical moving unit.
The tool 26 has a cutting tip 27 at the end thereof and is
positioned almost perpendicular to the surface of a polishing pad
24 arranged on the rotary surface table 22 of the CMP system. The
horizontal moving unit has a horizontal slide arm 32 holding the
tool 26 at a first end thereof and moving the tool 26 in a
direction almost parallel to the surface of the polishing pads 24.
The horizontal moving unit also has a horizontal casing 34 forming
a horizontal movement guide path for the horizontal moving arm 32.
That is, the horizontal casing 34 is connected to the second end of
the horizontal slide arm 32 and has a guide rail for guiding a
horizontal movement of the slide arm 32 relative to the horizontal
casing 34. The horizontal moving unit further includes a drive unit
for horizontally moving the slide arm 32 along the guide rail of
the horizontal casing 34. The base unit 42 supports the horizontal
casing 34 of the horizontal moving unit. The vertical moving unit
has a first level screw 28 adjusting a vertical position of the
tool 26 relative to the surface of the polishing pad 24.
[0032] The conditioning apparatus 50 also has an inclination
control unit for adjusting the angle of inclination of the
horizontal movement guide path for the horizontal slide arm 32
relative to the surface of the polishing pads 24. As shown in FIG.
2, the inclination control unit comprises a second level screw 38
provided at the base unit 42, and a hinge joint 36 connecting a
predetermined portion of the horizontal casing 34 to the base unit
42. The inclination control unit thus precisely controls the angle
of inclination of the movement path of the horizontal slide arm 32,
moving along the guide rail of the horizontal casing 34, relative
to the surface of the polishing pad 24.
[0033] FIGS. 3a and 3b are side views of tools 26 used in the
conditioning apparatus 50 of this invention.
[0034] In the tool 26 of FIG. 3a, the cutting edge is machined to
have a rake angle of about 90.degree., and is provided with a
cutting tip 27. In the present invention, a diamond tip having high
hardness is preferably used as the cutting tip 27. In the preferred
embodiment, a diamond having a diameter of about 1 mm is used as
the cutting tip 27. In the tool 26 of FIG. 3b, the cutting edge is
machined to have a relief angle of about 6.degree. suitable for
smoothly discharging chips from the cutting edge during a
conditioning process.
[0035] The operational effect of the conditioning apparatus 50 of
this invention will be described herein below in conjunction with
FIG. 2.
[0036] In order to condition a polishing pad 24 using the
conditioning apparatus 50, the tool 26 having the cutting tip 27 is
primarily positioned on the central portion of the surface of the
polishing pad 24 so as to set a conditioning start point on the pad
24. Of course, the conditioning start point on the pad 24 may be
determined by positioning the tool 26 on the outside surface of the
polishing pad in place of the inside surface. However, the rotating
force of the pad 24 is stronger at the outside surface than the
inside surface, and so The position of the tool 26 may be
undesirably changed at the initial stage of the conditioning
process. Therefore, it is preferable to position the tool 26 on the
inside surface of the pad 24 rather than the outside surface when
setting the conditioning start point.
[0037] Thereafter, the first level screw 28 is operated to move the
tool 26 in a vertical direction, thus precisely determining a
target depth of cut in the pad 24 to be desirably flattened. In
such a case, the term "target depth of cut" in the pad 24 denotes a
minimum depth to which the surface of the pad 24 is cut by the
cutting tip 27 of the tool 26 during the conditioning process. Such
a target depth of cut is determined by the vertical position of the
cutting tip 27 relative to the surface of the pad 24, and so it is
possible to precisely control the target depth of cut in the pad 24
by moving the tool 26 in the vertical direction by an operation of
the first level screw 28. In the present invention, it is
preferable to design the first level screw 28 such that the screw
28 is moved in the unit of .mu.m for accomplishing a desired
surface precision of the pad 24.
[0038] After determining the target depth of cut in the polishing
pad 24, the rotary surface table 22 is rotated about the center
thereof, thus rotating the pad 24 at a desired rotating velocity,
for example, 150.about.300 rpm. During such a rotation of the
polishing pad 24, the horizontal slide arm 32 is moved horizontally
along the guide rail of the horizontal casing 34 by the drive unit,
thus moving the tool 26 on the surface of the pad 24 in a direction
parallel to the surface of the pad 24 by a radius of the pad 24 or
longer distance. In such a case, the tool 26 is horizontally moved
on the surface of the rotating pad 24 at a velocity of several ten
millimeters per minute. In addition, such a horizontal moving
velocity of the tool 26 is almost constantly maintained during the
conditioning process, thus uniformly cutting the entire surface of
the pad 24 to accomplish a desired flatness of the pad 24.
[0039] The horizontal moving velocity of the tool 26 on the surface
of the pad 24 is determined in accordance with the rotating
velocity of the pad 24 such that the entire surface of the pad 24
is sufficiently cut to the target depth by the cutting tip 27. When
the rotating velocity of the pad 24 is higher than a reference
level, the horizontal moving velocity of the tool 26 is increased
to increase the cutting speed. However, the position of the tool 26
may be changed in accordance with the rotating velocity of the
polishing pad 24, and so it is preferable to limit the maximum
rotating speed of the pad to several hundred rpm. Particularly when
the target depth of cut in the pad 24 is set to a high level, a
high rotating velocity of the polishing pad 24 may deteriorate work
efficiency during the conditioning process. The determination of
both the rotating velocity of the polishing pad 24 and the
horizontal moving velocity of the tool 26 according to the target
depth of cut in the pad 24 is well known to those skilled in the
art, and further explanation is thus not deemed necessary.
[0040] In an experiment, a conditioning process using the apparatus
50 of this invention was performed at the rotating velocity of the
polishing pad set to about 180 rpm and the horizontal moving
velocity of the tool set to about 50 mm/min. The conditioning
apparatus using the tool of this invention finished the
conditioning process within above 5 minutes different from a
conventional disc-type diamond conditioner consuming about 15
minutes for finishing the process.
[0041] In the conditioning process of this invention, it is very
important to make the tool horizontally move in a direction
parallel to the surface of a polishing pad for accomplishing a
desired flatness of the pad's surface. Such a horizontal movement
of the tool relative to the surface of the polishing pad is
accomplished by arranging both the horizontal slide arm and the
guide rail of the horizontal casing such that they are positioned
in parallel to the pad's surface. However, the tool may sometimes
fail to move horizontally in parallel to the pad's surface due to a
structural deformation of the horizontal moving unit caused by an
external force or the condition of the pad laid on the rotary
surface table. In order to overcome such a problem, the
conditioning apparatus of this invention has the inclination
control unit.
[0042] The inclination control unit comprises the hinge joint 36
and the second level screw 38 as shown in FIG. 2. When it is
desired to control the angle of inclination of the movement path of
the horizontal slide arm 32 relative to the surface of the
polishing pad 24 and make the tool 26 horizontally move in a
direction parallel to the pad's surface, the end of the horizontal
casing 34 hinged to the base unit 42 is moved in a vertical
direction by an operation of the second level screw 38 provided at
the end of the base unit 42.
[0043] As described above, the present invention provides an
apparatus and method of conditioning the polishing pads of a CMP
system. In order to condition the surface of a polishing pad of the
CMP system, a tool with a cutting tip is primarily positioned on an
inside or outside surface of the polishing pad. Thereafter, the
tool is moved in a vertical direction so as to align the cutting
tip of the tool with a target depth of cut in the pad. The
polishing pad is rotated around its center, while the tool is moved
on the pad in a direction parallel to the surface of the pad during
the rotation of the pad. Therefore, the conditioning apparatus and
method of this invention precisely determines a target depth of cut
in the polishing pad by moving the tool in a vertical direction
using a first level screw, thus allowing the tool to precisely
flatten the surface of the polishing pad. In addition, the
apparatus and method of this invention quickly and uniformly
flattens the entire surface of the polishing pad by moving the tool
on the pad's surface in a horizontal direction while rotating the
pad.
[0044] Although a preferred embodiment of the present invention has
been described for illustrative purposes, those skilled in the art
will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
* * * * *