U.S. patent application number 12/191959 was filed with the patent office on 2010-02-18 for method for an improved chemical mechanical polishing system.
Invention is credited to Roy Nangoy, Yulin Wang, Alpay Yilmaz.
Application Number | 20100041316 12/191959 |
Document ID | / |
Family ID | 41669549 |
Filed Date | 2010-02-18 |
United States Patent
Application |
20100041316 |
Kind Code |
A1 |
Wang; Yulin ; et
al. |
February 18, 2010 |
METHOD FOR AN IMPROVED CHEMICAL MECHANICAL POLISHING SYSTEM
Abstract
A method for polishing a substrate on a pad large enough to
accommodate polishing at least two substrates simultaneously The
method includes simultaneously pressing a first substrate and a
second substrate against a single polishing surface of a polishing
module, providing polishing fluid from a first fluid delivery arm
in front of the first substrate while the first substrate is
pressed against the polishing surface, providing polishing fluid
from a second fluid delivery arm at a location in front of the
second substrate while the second substrate is pressed against the
polishing surface, conditioning the polishing surface with a first
conditioner at a location behind the first substrate while the
first substrate is pressed against the polishing surface, and
conditioning the polishing surface with a second conditioner at a
location behind the second substrate while the second substrate is
pressed against the polishing surface.
Inventors: |
Wang; Yulin; (Sunnyvale,
CA) ; Nangoy; Roy; (Santa Clara, CA) ; Yilmaz;
Alpay; (San Jose, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP - - APPM/TX
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Family ID: |
41669549 |
Appl. No.: |
12/191959 |
Filed: |
August 14, 2008 |
Current U.S.
Class: |
451/37 |
Current CPC
Class: |
B24B 53/017 20130101;
B24B 37/042 20130101; H01L 21/3212 20130101 |
Class at
Publication: |
451/37 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Claims
1. A method for polishing a substrate on a pad, comprising:
simultaneously pressing a first substrate and a second substrate
against a single polishing surface of a polishing module; providing
a first polishing fluid from a first fluid delivery arm at a
location in front of the first substrate while the first substrate
is pressed against the polishing surface; providing a second
polishing fluid from a second fluid delivery arm at a location in
front of the second substrate while the second substrate is pressed
against the polishing surface; conditioning the polishing surface
with a first conditioner at a location behind the first substrate
while the first substrate is pressed against the polishing surface;
and conditioning the polishing surface with a second conditioner at
a location behind the second substrate while the second substrate
is pressed against the polishing surface.
2. The method of claim 1, further comprising using end point
detection to determine a removal rate of a metal layer on at least
one of the two substrates.
3. The method of claim 2, wherein the metal layer is a copper
layer.
4. The method of claim 1, wherein a polishing rate is from about
3000 .ANG./min to about 12000 .ANG./min.
5. The method of claim 2, wherein the end point detection includes
eddy current endpoint detection or In Situ Removal Monitor (ISRM)
laser endpoint detection.
6. The method of claim 1, further comprising conditioning a region
of the polishing pad, where a previously polished substrate was
located, with additional polishing fluid before the region contacts
a next substrate.
7. The method of claim 6, wherein the conditioner has a sweeping
frequency within a range from about 12 swp/min to about 25
swp/min.
8. The method of claim 6, wherein the conditioner has a rotation
rate within a range from about 80 rpm to about 150 rpm.
9. The method of claim 6, wherein slurry agent is used as
additional polishing fluid.
10. The method of claim 9, wherein the slurry agent is silica.
11. The method of claim 9, wherein the slurry usage rate per slurry
delivery arm has a rotation rate within a range from about 300 sccm
to about 600 sccm,
12. The method of claim 9, wherein the slurry delivery arm sweeps
the polishing surface with a frequency rate within a range from
about 10 swp/min to about 60 swp/min.
13. The method of claim 9, wherein the slurry delivery arm has a
range within about 7 inches to about 13 inches.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the present invention generally relate to a
chemical mechanical polishing system suitable for use in
semiconductor manufacturing.
[0003] 2. Description of the Related Art
[0004] In semiconductor substrate manufacturing, the use of
chemical mechanical polishing, or CMP, has gained favor due to the
widespread use of damascene interconnects structures during
integrated circuit (IC) manufacturing. Although many commercially
available CMP systems have demonstrated robust polishing
performance, the move to smaller line widths requiring more precise
fabrication techniques, along with a continual need for increased
throughput and lower cost of consumables, drives and ongoing effort
for polishing system improvements. Moreover, most conventional
polishing systems have relatively limited flexibility for changes
to processing routines, thereby limiting the diversity of processes
that may be run through a single tool. Thus, certain new processing
routines may require new or dedicated tools, or costly downtime for
substantial tool configuration changes.
[0005] Therefore, there is a need for an improved chemical
mechanical polishing system.
SUMMARY OF THE INVENTION
[0006] The present invention generally provides a method for
polishing a substrate on a pad large enough to accommodate
polishing at least two substrates simultaneously. In one
embodiment, a method for polishing includes simultaneously pressing
a first substrate and a second substrate against a single polishing
surface of a polishing module, providing polishing fluid from a
first fluid delivery arm in front of the first substrate while the
first substrate is pressed against the polishing surface, providing
polishing fluid from a second fluid delivery arm at a location in
front of the second substrate while the second substrate is pressed
against the polishing surface, conditioning the polishing surface
with a first conditioner at a location behind the first substrate
while the first substrate is pressed against the polishing surface,
conditioning the polishing surface with a second conditioner at a
location behind the second substrate while the second substrate is
pressed against the polishing surface, and polishing the first and
second substrates in the presence of the fluids dispensed from the
first and second delivery arms.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0008] FIG. 1 is a top plan view of one embodiment of a chemical
mechanical polishing system;
[0009] FIG. 2 is a partial side view of a polishing station of FIG.
1 according to one embodiment of the invention; and
[0010] FIG. 3 is a flow chart of a method for simultaneously
polishing multiple substrates that may be practiced in the one
embodiment according to the invention.
[0011] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
and features of one embodiment may be beneficially incorporated in
other embodiments without further recitation.
[0012] It is to be noted, however, that the appended drawings
illustrate only exemplary embodiments of this invention and are
therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
DETAILED DESCRIPTION
[0013] Embodiments of the present invention provide methods and
apparatus for an improved chemical mechanical polishing system.
[0014] FIG. 1 is a top plan view illustrating one embodiment of a
chemical mechanical polishing ("CMP") system 100. The CMP system
100 includes a factory interface 102, a cleaner 104 and a polishing
module 106. A wet robot 108 is provided to transfer substrates 170
between the factory interface 102 and the polishing module 106. The
wet robot 108 may also be configured to transfer substrates between
the polishing module 106 and the cleaner 104. The factory interface
102 includes a dry robot 110 which is configured to transfer
substrates 170 between one or more cassettes 114 and one or more
transfer platforms 116. In one embodiment depicted in FIG. 1, four
substrate storage cassettes 114 are shown. The dry robot 110 has
sufficient range of motion to facilitate transfer between the four
cassettes 114 and the one or more transfer platforms 116.
Optionally, the dry robot 110 may be mounted on a rail or track 112
to position the robot 110 laterally within the factory interface
102, thereby increasing the range of motion of the dry robot 110
without requiring large or complex robot linkages. The dry robot
110 additionally is configured to receive substrates from the
cleaner 104 and return the clean polish substrates to the substrate
storage cassettes 114. Although one substrate transfer platform 116
is shown in the embodiment depicted in FIG. 1, two or more
substrate transfer platforms may be provided so that at least two
substrates may be queued for transfer to the polishing module 106
by the wet robot 108 at the same time.
[0015] Still referring to FIG. 1, the polishing module 106 includes
a plurality of polishing stations 124 on which substrates are
polished while retained in one or more polishing heads 126. The
polishing stations 124 are sized to interface with two or more
polishing heads 126 simultaneously so that polishing of two or more
substrates may occur using a single polishing station 124 at the
same time. The polishing heads 126 are coupled to a carriage 220
(shown in FIG. 2) that is mounted to an overhead track 128 that is
shown in phantom in FIG. 1. The overhead track 128 allows the
carriage 220 to be selectively positioned around the polishing
module 106 which facilitates positioning of the polishing heads 126
selectively over the polishing stations 124 and load cup 122. In
the embodiment depicted in FIG. 1, the overhead track 128 has a
circular configuration which allows the carriages 220 retaining the
polishing heads 126 to be selectively and independently rotated
over and/or clear of the load cups 122 and the polishing stations
124. The overhead track 128 may have other configurations including
elliptical, oval, linear or other suitable orientation and the
movement of the polishing heads 126 may be facilitated using other
suitable devices.
[0016] In one embodiment depicted in FIG. 1, two polishing stations
124 are shown located in opposite corners of the polishing module
106. At least one load cup 122 is in the corner of the polishing
module 106 between the polishing stations 124 closest the wet robot
108. The load cup 122 facilitates transfer between the wet robot
108 and the polishing head 126. Optionally, a third polishing
station 124 (shown in phantom) may be positioned in the corner of
the polishing module 126 opposite the load cups 122. Alternatively,
a second pair of load cups 122 (also shown in phantom) may be
located in the corner of the polishing module 106 opposite the load
cups 122 that are positioned proximate the wet robot. Additional
polishing stations 124 may be integrated in the polishing module
106 in systems having a larger footprint.
[0017] Each polishing station 124 includes a polishing surface 130
capable of polishing at least two substrates at the same time and a
matching number of polishing units for each of the substrates. Each
of the polishing units includes a polishing head 126, a
conditioning module 132 and a polishing fluid delivery module 134.
In one embodiment, the conditioning module 132 may be a conditioner
which dresses the pad by removing polishing debris and opening the
pores of the pad. In another embodiment, the polishing fluid
delivery module 134 may be a slurry delivery arm. The polishing
surface 130 is supported on a platen assembly (not shown) which
rotates the polishing surface 130 during processing. In one
embodiment, the polishing surface 130 is suitable for at least one
of a chemical mechanical polishing and/or an electrochemical
mechanical polishing process. In another embodiment, the platen may
be rotated during polishing at a rate from about 10 rpm to about
150 rpm, for example, about 50 rpm to about 110 rpm, such as about
80 rpm to about 100 rpm.
[0018] FIG. 2 is a partial side view showing one embodiment of one
of the polishing stations 124 of FIG. 1. Only one of the two or
more polishing units is shown in FIG. 2 for ease of explanation. In
the embodiment depicted in FIG. 2, a platen assembly 200 supports a
dielectric polishing pad 204. The upper surface of the pad 204
forms the polishing surface 130. The platen 202 is movably
supported on an inner frame 203 by one or more bearings 212. The
platen 202 is coupled by a shaft 206 to a motor 208 that is
operable to rotate the platen assembly 200. The motor 208 may be
coupled by a bracket 210 to the inner frame 203. In one embodiment,
the motor 208 is a direct drive motor. Other motors may also be
utilized to rotate the shaft 206. In one embodiment depicted in
FIG. 2, the motor 208 is utilized to rotate the platen assembly 200
such that the pad 204 retained thereon is rotated during processing
while the substrate 170 is retained against the polishing surface
130 by the polishing head 126.
[0019] In one embodiment, the polishing head 126 is rotated at a
rate from a range of about 10 rpm to about 150 rpm, for example,
about 50 rpm to about 110 rpm, such as about 80 rpm to about 100
rpm. The polishing head 126 may press the substrate 170 against the
pad 204 at a pressure in range of about 0.5 psi to about 5.0 psi,
for example, about 1 psi to about 4.5 psi, such as about 1.5 psi to
about 4.0 psi, for example. The polishing head 126 may have a
moving range preferably from about 10 to 14 inches. The polishing
head 126 may be sweeping from a frequency of about 1 sweep per
minute (swp/min) to about 40 swp/min, for example, about 5 swp/min
to about 30 swp/min, such as about 12 swp/min to about 25 swp/min.
Each sweep may be about 10 to about 14 inches.
[0020] The platen assembly 200 is large enough to support a
polishing pad 204 which will accommodate polishing of at least two
substrates retained by different polishing heads 126 and served by
different polishing units. In one embodiment, the dielectric
polishing pad 204 has a diameter greater than about 30 inches, for
example, between about 30 and about 52 inches, such as 42 inches.
Even though the dielectric polishing pad 204 may be utilized to
polish two substrates simultaneously, the pad unit area per number
of substrate simultaneously polished thereon is much greater than
conventional single substrate pads, thereby allowing the pad
service life to be significantly extended.
[0021] During processing or when otherwise desired, the
conditioning module 132 may be activated to contact and condition
the polishing surface 130. Additionally, polishing fluid is
delivered through the polishing fluid delivery module 134 to the
polishing surface 130 during processing. The distribution of
polishing fluid provided by the polishing fluid delivery module 134
may be selected to control the distribution of polishing fluid
across the lateral surface of the polishing surface 130. It should
be noted that while only one polishing head 126, conditioning
module 132 and polishing fluid delivery module 134 are depicted in
FIG. 2, more numbers of polishing heads and conditioning modules,
polishing fluid delivery modules are possible. For the sake of
clarity, there is sufficient room to accommodate at least one
additional polishing unit on the pad 204, as shown in FIG. 1. One
embodiment includes at least two sets of polishing heads 126,
conditioning modules 132 and polishing fluid delivery modules 134
working simultaneously to accommodate for the polishing of at least
two substrates simultaneously on one polishing pad 204.
[0022] The methods of the present invention will now be described
in detail below. It should be understood that each of the methods
of the present invention may be practiced on a single or a
multi-pad system. It should also be noted that different layers of
metal may be polished using the same method. In one embodiment, the
metal layer may be a copper layer. FIG. 3 is a flowchart of a
method for simultaneously polishing multiple substrates on a single
polishing surface that may be practiced in any polishing station
embodiments described herein. The polishing method may be practiced
in other suitable adapted systems, including those from the
equipment manufacturers. The method 300 begins at step 310, wherein
a first substrate and a second substrate are pressed against a
single polishing surface 130 of a polishing module 106 while the
surface 130 is rotated. At step 320, while the first substrate is
pressed against the polishing surface 130, a first slurry delivery
arm 134 in front of the first substrate delivers a polishing liquid
to the surface 130 in front of the first substrate. As a point of
reference, the area of the pad to be rotated under the substrates
is the "front" while the area of the pad just rotated from below
the substrate is the "back." In one embodiment, the polishing fluid
may be delivered to the pad surface 130 from the first slurry
delivery arm 134 at a rate of about 100 sccm to about 1000 sccm,
for example, about 200 sccm to about 800 sccm, such as about 300
sccm to about 600 sccm from each arm. At step 330, while the second
substrate is pressed against the polishing surface 130, a second
slurry delivery arm 135 in front of the second substrate delivers a
polishing fluid to the area in front of the second substrate. The
second slurry delivery arm 135 may provide fluid to the pad at
substantially the same rate as the first arm 134.
[0023] Additionally, the overall amount of slurry used per
substrate may be reduced since both the substrates and the pad are
polished with the same slurry agent. As a result, a reduced amount
of slurry may be used to polish the next substrate. In one
embodiment, silica may be used as the slurry agent. The parameters
for the slurry usage rate per slurry delivery arm may be range from
about 100 sccm to about 1000 sccm, for example, for about 200 sccm
to about 800 sccm, such as about 300 sccm to about 600 sccm. The
slurry delivery arm may sweep the polishing surface with a
frequency from a range of about 1 swp/min to about 70 swp/min,
preferably, for about 5 swp/min to about 60 swp/min, and more
preferably, for about 10 swp/min to about 60 swp/min, for example.
The movement of the slurry delivery arm may be from a range of
about 2 inches to about 18 inches, for example, for about 6 inches
to about 16 inches, such as about 7 inches to about 13 inches.
[0024] At step 360, the first and second substrates are polished in
the presence of the polishing fluid. Conditioning may occur before,
during or after polishing. Conditioning while polishing has shown
good results. While the substrate has been polished in the presence
of the polishing fluid, an end point detection device coupled with
the polishing station may be used to determine the removal rate of
the metal layer. In one embodiment, eddy current endpoint detection
may be used to monitor the removal rate of the metal layer. In
another embodiment, optical techniques, such as In Situ Removal
Monitor (ISRM) laser endpoint detection may be used to monitor the
removal rate of material from the substrate and/or to detect the
polishing endpoint.
[0025] At step 340, while the first substrate is still pressed
against the polishing surface 130, the polishing surface 130 is
conditioned with a first conditioner 132 at a location behind the
first substrate. In step 350, while the second substrate is still
pressed against the polishing surface 130, the polishing surface is
conditioned with a second conditioner 133 at a location behind the
second substrate.
[0026] Thus, as one region of the pad 204 against which one
substrate is currently pressed and polished, rotates out from under
the one substrate, this same region of the pad 204 is conditioned
prior to contacting a next substrate. In one embodiment, the
conditioner may include a diamond-containing surface that is swept
across the polishing surface at a frequency of about 1 swp/min to
about 40 swp/min, for example, about 5 swp/min to about 30 swp/min,
such as about 12 swp/min to about 25 swp/min. The conditioner may
have a sweep distance of about 0.5 to about 21 inches, for example,
1.0 to about 20 inches. The conditioner may rotate the
diamond-containing surface against the pad 304 at a rotation rate
of about 10 rpm to about 300 rpm, for example, about 50 rpm to
about 200 rpm, such as about 80 rpm to about 150 rpm, for
example.
[0027] In one embodiment, each substrate may be polished utilizing
a two-step process. A first step includes removing the bulk
thickness of copper followed by a copper clearance step. The bulk
removal step ends at or about when the underlying material begins
to be exposed through the copper layer. In one embodiment, the bulk
removal step may remove copper at a polishing rate of between about
9,000 to about 10,000 .ANG./min. The platen speed may be maintained
between about 83 to 113 revolutions per minute (rpm) while the head
is rotated between about 77 and about 107 revolutions per minute.
The polishing head may be oscillated with a frequency of about 19
sweeps per minute through a distance of between 10 to about 14
inches. The substrate is pressed against the polishing surface at a
pressure of between about 2.2 to about 2.9 psi. A low silica
content slurry having neutral pH may be utilized at about 300 sccm
per slurry delivery arm. The slurry delivery arm may be swept
between about 9 to 11 inches with a frequency of 19 to about 38
sweeps per minute. During polishing, the conditioner may be pressed
against the pad with a force of between about 3 to about 5 psi
while being rotated at about 108 rpm. The conditioner may be swept
over a distance of about 1.5 to about 20 inches.
[0028] The copper clearance step may remove copper to expose a
barrier layer at a rate of between 4,000 to 5,000 .ANG./min. During
the copper clearance step, the platen may be rotated about 83 to
113 revolutions per minute while the polishing head is rotated
between about 77 to about 107 rotations per minute. The substrate
is pressed against the polishing pad with a force of between 1.1 to
about 1.3 psi while the head is swept over a distance of about 10
to about 14 inches with a frequency of about 19 sweeps per minute.
A low silica content polishing slurry having neutral pH may be
provided at a rate of about 2 sccm per slurry delivery arm. The
slurry delivery arm may be swept over a distance of about 9 to
about 12 inches with a frequency of 19 to about 38 sweeps per
minute. The conditioner may be pressed against the polishing
surface while processing substrate with a force of between about 3
psi to about 5 psi while rotating the conditioner with an rpm of
about 108, while sweeping the conditioner over a distance between
about 1.5 to about 20 inches.
[0029] The invention provides an improved method for the CMP
process by providing a pad large enough to accommodate polishing at
least two substrates simultaneously while also providing a clean
and conditioned polishing surface after each polishing of the
substrates. Copper polish rates up to about 20,000 Angstrom per
minute (.ANG./min) may be obtained, for example, about 2,000
.ANG./min to about 15,000 .ANG./min, such as about 3,000 .ANG./min
to about 12,000 .ANG./min, for example, have been realized with
good match of substrate to substrate results. Thus, the improved
polishing repeatability and extended life of the polishing surface
is advantageously obtained.
[0030] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *