U.S. patent application number 12/685467 was filed with the patent office on 2010-07-15 for polishing pads for chemical mechanical planarization and/or other polishing methods.
This patent application is currently assigned to Novaplanar Technology, Inc.. Invention is credited to Michael R. Oliver.
Application Number | 20100178853 12/685467 |
Document ID | / |
Family ID | 42317192 |
Filed Date | 2010-07-15 |
United States Patent
Application |
20100178853 |
Kind Code |
A1 |
Oliver; Michael R. |
July 15, 2010 |
POLISHING PADS FOR CHEMICAL MECHANICAL PLANARIZATION AND/OR OTHER
POLISHING METHODS
Abstract
Embodiments herein provide polishing pads that produce high
post-polish planarity, such as on a wafer substrate or other
substrates. Exemplary pads include a bulk matrix and embedded
polymer particles. Pads according to embodiments herein may be used
to remove material over a composite substrate, comprised of two or
more different materials, or a substrate comprised of a single
material.
Inventors: |
Oliver; Michael R.;
(Portland, OR) |
Correspondence
Address: |
Schwabe Williamson & Wyatt;PACWEST CENTER, SUITE 1900
1211 SW FIFTH AVENUE
PORTLAND
OR
97204
US
|
Assignee: |
Novaplanar Technology, Inc.
Portland
OR
|
Family ID: |
42317192 |
Appl. No.: |
12/685467 |
Filed: |
January 11, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61144004 |
Jan 12, 2009 |
|
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Current U.S.
Class: |
451/59 ;
451/526 |
Current CPC
Class: |
B24B 37/24 20130101 |
Class at
Publication: |
451/59 ;
451/526 |
International
Class: |
B24B 1/00 20060101
B24B001/00; B24D 11/00 20060101 B24D011/00 |
Claims
1. A polishing pad, comprising: a matrix comprising a siloxane
polymer having a loss factor, tan (.delta.), of at least 0.05; and
a plurality of polymer particles embedded within the matrix, the
polymer particles having a different chemical composition from that
of the matrix.
2. The polishing pad of claim 1, wherein the matrix has a storage
modulus of about 1.times.10.sup.5 Pa to about 1.times.10.sup.7 Pa
and a loss modulus of about 1.times.10.sup.4 Pa to about
1.times.10.sup.6 Pa.
3. The polishing pad of claim 1, wherein the polishing pad defines
a pad volume, and the polymer particles comprise approximately 10
to 30% of the pad volume.
4. The polishing pad of claim 1, wherein the polymer particles
comprise at least one of polyurethane, polyurea, polycarbonate,
polyether, polyester, polysulfone, polystyrene, polyamide,
polyacrylamide, polypropylene, polyethylene, polybutadiene,
polyvinyl chloride, polymethyl methacrylate, polyvinyl alcohol, and
nylon.
5. The polishing pad of claim 1, further comprising a supporting
layer coupled to the matrix.
6. The polishing pad of claim 5, wherein the supporting layer
comprises at least one of polyester, glass, nylon, rayon and
cotton.
7. The polishing pad of claim 1, wherein the matrix comprises at
least one groove or pattern in a surface thereof.
8. A polishing pad, comprising: a matrix comprising a material
having a storage modulus of about 1.times.10.sup.5 Pa to about
1.times.10.sup.7 Pa and a loss modulus of about 1.times.10.sup.4 Pa
to about 1.times.10.sup.6 Pa; and a plurality of polymer particles
embedded within the matrix and having a mean particle diameter of
approximately 10 to 100 .mu.m.
9. The polishing pad of claim 8, wherein the loss modulus of the
matrix material is about 1.times.10.sup.5 Pa.
10. The polishing pad of claim 8, wherein the matrix material
comprises a loss factor, tan (.delta.), of at least 0.05.
11. The polishing pad of claim 8, wherein the matrix material
comprises a loss factor, tan (.delta.), of at least 0.1.
12. The polishing pad of claim 8, wherein the polishing pad has a
thickness of 10 to 200 mils.
13. The polishing pad of claim 8, wherein the polymer particles are
randomly distributed in the matrix.
14. The polishing pad of claim 8, wherein the polymer particles are
relatively uniformly distributed throughout the matrix.
15. The polishing pad of claim 8, wherein the polishing pad defines
a pad volume, and the polymer particles comprise approximately 10
to 30% of the pad volume.
16. The polishing pad of claim 8, wherein the matrix material
comprises a siloxane polymer.
17. The polishing pad of claim 8, wherein the matrix material
comprises crosslinked polydimethylsiloxane.
18. The polishing pad of claim 8, wherein the matrix material
comprises fluorinated polydimethylsiloxane.
19. The polishing pad of claim 8, wherein the matrix further
comprises silica filler particles.
20. The polishing pad of claim 8, wherein the polymer particles
comprise at least one of polyurethane, polyurea, polycarbonate,
polyether, polyester, polysulfone, polystyrene, polyamide,
polyacrylamide, polypropylene, polyethylene, polybutadiene,
polyvinyl chloride, polymethyl methacrylate, polyvinyl alcohol, and
nylon.
21. The polishing pad of claim 8, wherein the polymer particles
comprise hydroxylated polyester particles.
22. The polishing pad of claim 21, wherein the hydroxylated
polyester particles have a mean particle diameter of approximately
60 .mu.m.
23. The polishing pad of claim 21, wherein the polishing pad
defines a pad volume, wherein the hydroxylated polyester particles
comprise approximately 20% of the volume of the pad.
24. The polishing pad of claim 8, further comprising a supporting
layer coupled to the matrix.
25. The polishing pad of claim 24, wherein the supporting layer
comprises at least one of polyester, glass, nylon, rayon and
cotton.
26. The polishing pad of claim 8, wherein the matrix comprises at
least one groove or pattern in a surface thereof.
27. A method of polishing a surface of a substrate, comprising:
providing a substrate; and contacting the substrate with a
polishing pad, whereby the polishing pad and/or the substrate are
moved relative to the other of the polishing pad and the substrate
while in contact, the polishing pad comprising: a matrix comprising
a material having a storage modulus of about 1.times.10.sup.5 Pa to
about 1.times.10.sup.7 Pa and a loss modulus of about
1.times.10.sup.4 Pa to about 1.times.10.sup.6 Pa; and polymer
particles embedded within the matrix and having a mean particle
diameter of approximately 10 to 100 .mu.m.
28. The method of claim 27, wherein the substrate has a line to be
polished, the line having a linewidth, and wherein the mean
particle diameter of the polymer particles is at least
approximately 2-20 times larger than the linewidth of the line to
be polished.
Description
TECHNICAL FIELD
[0001] Embodiments herein relate to polishing pads for chemical
mechanical planarization and/or for other polishing methods,
including polishing various surfaces/substrates.
BACKGROUND
[0002] Chemical Mechanical Planarization (CMP) is a method for
planarizing the surface of substrates in semiconductor processing.
CMP material removal occurs typically by simultaneous chemical and
mechanical interaction with the substrate. With CMP, a highly
planar surface may be obtained, which is very useful for many
semiconductor device structures.
[0003] One structure used in CMP is a polishing pad. Pads may
comprise a variety of materials and are used, sometimes in
conjunction with a polishing fluid (slurry) as the CMP interface
with the surface of a substrate. In general, polishing pads may be
used for CMP or for other polishing methods, including polishing
the surfaces of a variety of substrates.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Embodiments herein will be readily understood by the
following detailed description in conjunction with the accompanying
drawings. To facilitate this description, like reference numerals
designate like structural elements. Embodiments herein are
illustrated by way of example and not by way of limitation in the
figures of the accompanying drawings.
[0005] FIG. 1 illustrates a perspective view of a substrate
processing apparatus in accordance with a representative
embodiment;
[0006] FIG. 2 illustrates a cross-sectional view of a pad in
accordance with an embodiment;
[0007] FIG. 3 illustrates an expanded cross-sectional view of a
portion of the pad of FIG. 2 in accordance with an embodiment;
[0008] FIG. 4 illustrates a cross-sectional view of a pad in
accordance with an embodiment; and
[0009] FIG. 5 illustrates an exemplary schematic of a pad and
particle interacting with a substrate in accordance with an
embodiment.
DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS
[0010] In the following detailed description, reference is made to
the accompanying drawings which form a part hereof wherein like
numerals designate like parts throughout, and in which is shown by
way of illustration embodiments in which the invention may be
practiced. It is to be understood that other embodiments may be
utilized and structural or logical changes may be made without
departing from the intended scope. Therefore, the following
detailed description is not to be taken in a limiting sense, and
the scope of embodiments is defined by the appended claims and
their equivalents.
[0011] Various operations may be described as multiple discrete
operations in turn, in a manner that may be helpful in
understanding embodiments; however, the order of description should
not be construed to imply that these operations are order
dependent.
[0012] The description may use perspective-based descriptions such
as up/down, back/front, and top/bottom. Such descriptions are
merely used to facilitate the discussion and are not intended to
restrict the application of embodiments herein.
[0013] For the purposes of the description, a phrase in the form
"A/B" or in the form "A and/or B" means (A), (B), or (A and B). For
the purposes of the description, a phrase in the form "at least one
of A, B, and C" means (A), (B), (C), (A and B), (A and C), (B and
C), or (A, B and C). For the purposes of the description, a phrase
in the form "(A)B" means (B) or (AB) that is, A is an optional
element.
[0014] The description may use the phrases "in an embodiment," or
"in embodiments," which may each refer to one or more of the same
or different embodiments. Furthermore, the terms "comprising,"
"including," "having," and the like, as used with respect to
embodiments herein, are synonymous.
[0015] Embodiments herein provide polishing pads that produce high
post-polish planarity on a substrate. Pads according to embodiments
herein may be used to remove material over a composite substrate,
comprised of two or more different materials, or a substrate
comprised of a single material. While CMP is mentioned herein as a
suitable method for use of the described pads, use with other
polishing methods, including use on other substrates, is also
contemplated and within the scope of the embodiments.
[0016] In embodiments, polishing pads described herein may be used
to polish semiconductor materials, wafers, silicon, glass, metal,
microelectromechanical systems (MEMS), sapphire, etc.
[0017] In an exemplary embodiment referred to as copper CMP, the
copper and barrier layer on top of the dielectric may be removed,
and polishing may be terminated when the dielectric between the
copper conductors is completely exposed. It may also be terminated
when all of the copper is removed and only the thin barrier layer
remains.
[0018] In embodiments, a polishing pad may be fabricated from
silicone rubber, also referred to as siloxane polymer. In an
embodiment, a pad may have a bulk matrix, such as constructed, at
least in part, from a siloxane polymer, and may, in an embodiment,
contain embedded particles of a different material, such as
polyurethane.
[0019] In an embodiment, a pad constructed from a siloxane polymer
material is moderately compressible, having a storage modulus, E',
such as within a factor of ten of 1.times.10.sup.6 Pascals (Pa). In
embodiments, the storage modulus, E', and the loss modulus, E'',
may be varied over a moderate range for siloxane polymers. A
representative value for E' is about 1.times.10.sup.6 Pa for
siloxane polymers, but may range from about 1.times.10.sup.5 Pa to
1.times.10.sup.7 Pa, with a suitable sub-range falling between
about 2.times.10.sup.5 Pa and about 5.times.10.sup.6 Pa and more
particularly between above 4.times.10.sup.5 Pa and about
2.times.10.sup.6 Pa. In an embodiment, with decreasing density, the
storage modulus E' decreases. In an embodiment, a corresponding
suitable value for E'' is about 1.times.10.sup.4 Pa to about
1.times.10.sup.6 Pa, such as about 1.times.10.sup.5 Pa. In
embodiments, the above-described values may be suitable for pads
constructed from other bulk matrix materials.
[0020] In an embodiment, a polishing pad is provided comprising a
matrix comprising a material having a storage modulus of about
1.times.10.sup.5 Pa to about 1.times.10.sup.7 Pa and a loss modulus
of about 1.times.10.sup.4 Pa to about 1.times.10.sup.6 Pa; and
polymer particles embedded within the matrix and having a mean
particle diameter of approximately 10 to 100 .mu.m.
[0021] The mechanical properties of the bulk siloxane polymer
matrix primarily determine the mechanical response of the pad.
These properties may be controlled, for example, by changing the
composition and/or density of the bulk polymer and/or the embedded
particles. In embodiments, both E' and E'' may be varied
significantly by changing the chemistry of the starting materials
when making a siloxane polymer. These properties may also be
modified by the addition of particles, such as small fumed silica
particles. Such particles may be added to increase E'.
[0022] When compressed, pads in accordance with embodiments rebound
slowly enough to produce a low defect surface with low dishing, and
thus highly planar polished surfaces on composite structures. A pad
in accordance with embodiments herein may be dissipative, having a
loss factor, tan .delta., of about 0.1. The loss factor, tan
.delta., is the ratio of the loss modulus, E'', to the storage
modulus, E'. In embodiments, tan .delta. may be at least about 0.05
and, in other embodiments, may be greater than about 0.1.
[0023] In an embodiment, a polishing pad is provided comprising a
matrix comprising a siloxane polymer having a loss factor of at
least 0.05; and a plurality of polymer particles embedded within
the matrix, the polymer particles having a different chemical
composition from that of the matrix.
[0024] In an embodiment, a siloxane polymer may create a mechanical
response at the pad surface, especially the local slow rebound of
the pad surface which may produce a high planarity of the finished
substrate. In an embodiment using a siloxane polymer, the loss
factor increases with increasing frequency (decreasing time). This
loss response produces a mechanical response of a pad in which the
pad is not capable of quickly providing an upward force beyond the
plane of the surface being polished thus beneficially inhibiting
the creation of topography in the material being polished. For
typical CMP operating conditions, these properties result in a very
planar final surface with low defect level, even when the substrate
is a composite of multiple types of materials.
[0025] Pads in accordance with embodiments herein may be utilized
to polish surfaces of one material, such as silicon or glass, as
well as for surfaces of two or more materials such as encountered
in CMP of semiconductors. The beneficial polishing characteristics
are enabled by (1) the low E' of the bulk matrix that results in a
small additional increase in local force per unit area when the pad
is compressed, and (2) the properties of the pad that do not allow
the polymer particles within it to be pushed well above the
polishing plane. The mechanical properties of the pad restrict the
pad from driving itself into the material being polished, and
restrict it from pushing slurry particles well beyond the polishing
plane. The combination of these properties reduces the capability
of the pad to provide a strong, localized pressure beyond the
polishing plane, which is a key mechanism for defect generation in
a surface being polished.
[0026] While siloxane polymers may be formed from
polydimethylsiloxane (PDMS)-based precursors, the length of the
starting chains may be modified as desired. In an embodiment, some
fraction of the methyl side groups on the siloxane chain may be
substituted with other moieties. Such substitution may affect the
amount of crosslinking between siloxane chains. Other factors, such
as the catalyst used and the curing process, may also affect the
chemical interaction of crosslinking. For most polishing processes,
a high degree of crosslinking is desirable. Thus, in accordance
with the teachings herein, a siloxane material chemistry may be
formulated to optimize E' and E'' for a given application.
[0027] In addition to the chemical processes discussed above, in
embodiments, siloxane polymers may also be produced as a sponge or
a foam, for example, with pockets of gas contained within the
polymer matrix. In an embodiment, a suitable gas may be air,
nitrogen, or another suitable gas. For example, with a sufficient
addition of foaming chemistry to the starting materials, enough gas
may be created. This may result in the gas pockets being
interconnected, producing what is known as open-celled foam. Thus,
the capability to add varying amounts of foaming agents to the
starting materials allows for the formulation of a wide range of
foam densities. In an embodiment, a foam may be created by
reactions occurring during a curing process at a suitable curing
temperature.
[0028] There is a wide range of final structures of siloxane
polymers that may be fabricated in accordance with embodiments
described herein. Further details of such polymers may be found in
Siloxane Polymers, by Clarson and Semlyen (1993), the contents of
which are hereby incorporated by reference.
[0029] In an embodiment, a pad may have a bulk matrix, such as
constructed, at least in part, from a siloxane polymer. The bulk
matrix of a pad in accordance with an embodiment may be siloxane
polymer, including, for example, polydimethylsiloxane and chemical
variants thereof (such as crosslinked and/or fluorinated
polydimethylsiloxane), or combinations of more than one
polymer.
[0030] In an embodiment, a bulk matrix may also contain particles
of a different material, such as polyurethane. In such embodiments,
these particles, when they are exposed at the pad surface, may be
the primary or sole locus of the interaction of the pad with the
substrate to be polished or with the polishing fluid/slurry being
utilized. Suitable particles generally have adequate surface energy
and may further be used to enhance the polish interface between the
pad and the substrate. In an embodiment, the particles may abrade
more slowly than the bulk material such that the particles serve as
the primary source of contact with the substrate.
[0031] In an embodiment, a preferred particle type is a polymer,
such as polyurethane, which is widely used as a bulk material for
CMP pads. In an embodiment, it may be used as a surface material
where the polishing interaction between the pad and the substrate
takes place. In embodiments, other types of particles, such as
polyurea, polycarbonate, polyether, polyester, hydroxylated
polyester, polysulfone, polystyrene, polyamide, polyacrylamide,
polypropylene, polyethylene, polybutadiene, polyvinyl chloride,
polymethyl methacrylate, polyvinyl alcohol, or nylon, among others,
may be used as well. Suitable particles may be selected for their
properties at the pad-particle-wafer and/or the pad-particle-slurry
interface.
[0032] In an embodiment, polymer particles have a mean particle
diameter of approximately 10-100 .mu.m, such as 50-70 .mu.m, for
example 60 .mu.m. In an embodiment, a polymer pad defines a pad
volume, wherein the polymer particles comprise approximately
10-30%, such as approximately 20%, of the volume of the pad.
[0033] In embodiments, polymer particles may be randomly
distributed in the matrix, or further may be relatively uniformly
distributed throughout the matrix.
[0034] In an embodiment, there may be a distribution of the sizes
of particles within the pad matrix. In an embodiment, the particles
may be selected or controlled to be of a desired size or within a
desired size range. For example, particles may be filtered to
remove particles above and/or below a certain size, such as below
30 .mu.m.
[0035] In embodiments, one or more particle types/compositions may
be used as desired for embodiments herein. Using different particle
types may be advantageous, for example, for polishing more than one
type of material in a single substrate or in different substrates.
In embodiments, the particle material(s) may be matched to the
polishing fluids/slurries to be used and/or to the substrates to be
polished to maximize specific polishing effects of the pad. In an
embodiment, particles larger than a certain diameter may be used to
polish a surface having various features to ensure the particles do
not extend too far into such features (for example, a line on a
semiconductor) during polishing.
[0036] For polishing surfaces of only one material, such as silicon
or glass, there are no features on the object being polished that
suggest a limit on the size of the polymer particles within the
pad. In such an embodiment, any limitations on particle size occur
as part of optimization of the polishing process itself, i.e., the
polishing rate and the polishing uniformity may be modulated by the
size and density of the polymer particles within the pad. This
control allows the overall polishing process optimization with
respect to parameters including speed, cost and polishing figures
of merit such as uniformity.
[0037] In accordance with an embodiment, embedded pad particles
provide contact points between the pad, the substrate, and slurry
particles, or, for particle-free slurries, between the pad and the
substrate being polished. By using embedded particles in this
manner, in embodiments, certain functions of the pad may be
controlled separately. In an embodiment, the polymer particles of
the pad, which may be the primary contact points on the surface of
the pad, interact with the slurry particles and the substrate being
polished. The pad polymer particles may be selected for high CMP
material removal rate or other CMP performance criteria such as low
defect generation.
[0038] In an embodiment, the bulk mechanical response of the pad
may be separately adjusted by using one or more different materials
with different mechanical properties.
[0039] One exemplary desirable material for a CMP polishing pad is
a siloxane polymer. Its low storage modulus, E', and high loss
factor, tan .delta., may produce a highly planar final structure on
a polished composite substrate. A secondary material may also be
included within the polymer matrix in a density of, for example,
approximately 10-30% such as approximately 10%, 15%, 20%, or 30%.
In an embodiment, silica filler particles, or other filler
particles, may also be included in the bulk matrix to change some
bulk mechanical properties such as the storage modulus, E'.
[0040] Siloxane polymers formed from PDMS are generally
hydrophobic, with surface energies on the order of 20 mN/m. In an
embodiment, it is desirable for CMP to use a polishing fluid, or
slurry, to wet the interactive pad surface to provide for improved
CMP operation. In an embodiment, it is important that the local pad
surface where polishing occurs be wetted. For the polymer particles
noted above, they have higher surface energy than the siloxane
matrix. With polyurethane particles, for example, which have a
surface energy in the range of 40-50 mN/m, improved local wetting
occurs where the polishing action takes place. Other polymer
particle types, such as polycarbonate, polyester, etc., also
provide locally higher surface energy at the site of the polishing
process.
[0041] In an embodiment, the siloxane polymer itself may be made
more hydrophilic by chemical modifications to the PDMS starting
material. Substitution of one or more of the methyl groups in the
PDMS backbone by polyether or other groups may produce a higher
surface energy, and hence may make the polymer more
hydrophilic.
[0042] There are thus multiple approaches that may be used in
embodiments to improve the wettability of the surface of a siloxane
polymer-based pad. These include: 1) modification of the siloxane
matrix material by chemical addition/substitution, 2) incorporation
of higher surface energy particles into the pad material, resulting
in a heterogeneous structure, and 3) roughening the surface of the
pad.
[0043] In embodiments, methods of manufacturing siloxane polymer
objects include, but are not limited to calendering, compression
molding, spraying, dispersion, and extrusion.
[0044] One method that lends itself well to manufacture of
polishing pads for CMP is compression molding. In a compression
molding process, the uncured silicone rubber precursors, as well as
polishing particles, such as polyurethane, may be placed in the
mold, which may then be covered and heated. In an embodiment, the
top surface of the mold may have a pad groove design in it. After
the pad is formed, it may be cured in a separate oven.
[0045] Another method in accordance with an embodiment that lends
itself well to the manufacture of polishing pads for CMP is
calendering. In such an approach, the silicone polymer feed stock
is passed through sets of three or four rollers, and the material
is squeezed out into sheets of well-controlled thickness. For
example, sheets over one meter width may be made with this
approach. After exiting the last set of rollers, the polymer sheet
may be placed in a curing oven, where it may be given a controlled
thermal cure. The time and temperature of the cure cycle may be
determined by the incoming siloxane polymer chemistry and the
curing agent incorporated into the initial chemistry mix. The
separation between the final two rollers determines the thickness
of the sheet. Sheets may be cured, for example, after groove
patternings, or may be used as preforms for a molding process.
[0046] In an embodiment, a preferred thickness range for CMP pads
is in the range of 10-200 mils. Such a thickness range may be
achieved, for example, by calendering or molding.
[0047] In an embodiment, a siloxane polymer is quite flexible in
this thickness range (10-200 mils). In an embodiment, one method to
improve the plane stiffness may be to put the siloxane polymer on a
relatively stiff supporting material, such as when it goes through
the final pair of rollers in a calendering method. One useful
material for such an embodiment is polyester cloth, about 0.020''
thick, which has been cleaned and heatset. The structure resulting
from a calendering process as described above may incorporate the
permeable cloth as the bottom layer of a two-, or multi-, layer
structure. In embodiments, suitable materials, such as polyester,
glass, nylon, rayon or cotton, may be used to provide in-plane
stiffness, permeability, and/or thermal and chemical
robustness.
[0048] In a suitable calendering system, multiple layer structures
in accordance with embodiments may be created. For example, in an
embodiment, a structure may initially be created with a cloth layer
to provide high in-plane stiffness and an ungrooved, siloxane
polymer layer. In an embodiment, the multi-layer structure may then
be partially cured, and subsequently used as the bottom layer
between the final rollers when a second siloxane polymer layer is
added to the top of the structure. This top layer, which may be the
layer in contact with the slurry and wafer, or other surface to be
polished, may, in an embodiment, be grooved or ungrooved and may
have a composition different from the base layer.
[0049] In an embodiment, multiple layers of different materials may
be used to control the CMP planarization properties of the pad over
long distances across the surface of the wafer, and not just at the
interface between two materials on the composite surface of the
wafer. In embodiments, planarization lengths of several millimeters
may be achieved. Additional details regarding multiple layered pads
that may be incorporated with embodiments herein may be found in
U.S. Pat. No. 5,212,910, the entire contents of which are hereby
incorporated by reference.
[0050] In embodiments, CMP pads may have grooves or other
patterning in various configurations for improved polishing
performance. In embodiments, dimensions of spacing and groove depth
may be varied over a wide range. In an embodiment, suitable grooves
may be, for example, about 0.010 to about 0.050 inches deep and/or
wide. In an embodiment, suitable grooves may be spaced from about
0.020 to about 0.5 inches apart, in a variety of patterns, as
desired.
[0051] Grooves may be formed in a siloxane polymer pad in several
ways, such as by molding. In an embodiment, an uncured polymer may
be soft enough to emboss grooves into it by a patterned roller, or
by a stamp. In an embodiment, for a compression molded pad, the top
interior surface of the mold may have a raised pattern, so that the
pad is patterned when it exits the mold. Clearly, the pattern may
be whatever may be created with a raised structure on the mold
surface, for example square patterns, hexagonal patterns or
concentric grooves.
[0052] FIG. 1 illustrates a perspective view of a substrate
processing apparatus in accordance with an exemplary
embodiment.
[0053] A system 100 for chemical mechanical polishing may include a
rotating platen 102, which is driven through a drive shaft 104. A
polishing pad 106 is attached to the top surface of platen 102.
Polishing slurry 108 is dispensed on the pad from one or more
orifices 110 on the slurry dispensing arm 112. Wafer carrier 114
holds the wafer (with retaining ring) 116. Wafer 116, with the side
to be planarized face down, is pressed against the surface 118 of
polishing pad 106 and rotated by the carrier drive shaft 120.
[0054] Pad 210 is seen in cross section in FIG. 2 and represents an
exemplary embodiment. Top surface 216 of pad 210 is the polishing,
or planarizing, surface. Body 212 of pad 210 is composed of the
matrix material and polymer particles. Pad 210 is built on a
supporting cloth layer 220. Grooves 214 are cut into surface 216 of
pad 210 for proper slurry flow. Pad 210 may be attached to a platen
surface with an adhesive layer 218.
[0055] An exemplary expanded cross section of location 230 near top
surface 216 of pad 210 is shown in FIG. 3. The pad is composed of a
siloxane polymer matrix 302 and polymer particles 304. Pad surface
216 has some exposed polymer particles 306.
[0056] FIG. 4 shows a pad structure with two layers of matrix
material in accordance with an embodiment. Pad 400 is composed of a
supporting layer 404, such as constructed from polyester, glass,
nylon, rayon, or cotton, etc. in contact with a lower layer or base
pad 402 of material, constructed from foam, or a similarly
structured or functioning material. In an embodiment, lower layer
402 is compressible and may help compensate for pad height
variations. In an alternative embodiment, lower layer 402 may be
absent. Upper layer 406 is the bulk matrix material, such as
constructed from a siloxane polymer, in which pad surface 408 is
formed. Grooves 410 are formed in the second layer, but in an
embodiment may extend further into a lower layer or layers. The
entire structure has an adhesive layer 412 to provide contact, for
example, to a platen surface. The local polishing rate at any point
of the material on the wafer surface increases with increasing down
force between the wafer and the pad and with increasing relative
velocity between the wafer and the pad. Other parameters such as
the pad type and structure, as well as the chemistry and particles
of the slurry also determine the material removal rate. For
additional details regarding such parameters, see
Chemical-Mechanical Planarization of Semiconductor Materials, M. R.
Oliver (ed.), Springer Verlag, the entire contents of which are
hereby incorporated by reference.
[0057] Although the pads of FIGS. 2 and 4 are shown with grooves,
in embodiments, pads may be contructed without grooves or
patterning, or pads may have other surface patterning in addition
to or instead of the represented grooves.
[0058] Embodiments herein provide polishing with low dishing. Such
low dishing may be accomplished by one or both of two mechanisms of
action.
[0059] The first mechanism of action causing low dishing is based
on the mechanical properties of the matrix. The polymer particles
embedded in the low E', lossy pad do not rebound quickly to reach
down and polish in a recess during polishing. A polymer particle
meets the far side of a recessed structure in the horizontal
direction before the pad can push it down very far into the recess.
As a result, for narrow recesses, the surface of the polishing
polymer particle does not reach the bottom of the recess and no
further material is removed. This mechanism is particularly
effective for recesses of small lateral dimension, for example less
than 20 .mu.m, when the direction of polishing is substantially
across this short dimension.
[0060] When the direction of travel is along a much longer
dimension, such as a long conductor line, another mechanism may
come into play.
[0061] The second mechanism of action causing low dishing is based
on the size of the pad polymer particle. In embodiments, the
polymer polishing particles have large dimensions relative to the
narrow structures they are polishing. For example, a polymer
particle may have a diameter of .gtoreq.20 .mu.m or so, while at
the same time the long line being polished is very narrow. At
current technology levels, these are less than 5 .mu.m wide. As a
result, the particle, when it is on top of a narrow structure can
not reach down very far into a recess in that structure. This
limiting mechanism holds for the component of the relative velocity
of the particle along the long dimension of the structure being
polished. For conducting lines in a semiconductor structure, this
direction is along the length of the conductor.
[0062] The two limiting mechanisms both contribute to the
limitation of dishing, especially in the case of recessed
structures where the long and short dimensions are greatly
different. Both mechanisms are made possible by the large polymer
particles keeping their shape during polishing. This is in contrast
to a standard polymer pad, where narrow asperities are compressed
under very high pressure during polishing. When these asperities,
with their high E', reach a recess, the asperities very quickly
reach down into the recess. Results from the literature show this
is usually on the order of 1000-2000 .ANG., for processing with
standard pads and processes.
[0063] In an embodiment, polymer particles may have a mean diameter
at least approximately 2-20 times, such as approximately 2, 4, 6,
8, 10, 15, 20, or more times, larger than the linewidth of the
lines being polished by the pad.
[0064] FIG. 5 illustrates an exemplary schematic of a pad and
particle interacting with a substrate. Pad 502 has a polymer
particle 504. Polymer particle 504 is contacting a line 506 formed
in substrate 508. For example, line 506 may be a metal line and
substrate 508 may be a dielectric material. As may be seen, the
size of particle 504 relative to the linewidth prevents particle
504 from reaching down into line 506 to remove material beyond a
certain depth.
[0065] Although certain embodiments have been illustrated and
described herein for purposes of description of the preferred
embodiment, it will be appreciated by those of ordinary skill in
the art that a wide variety of alternate and/or equivalent
embodiments or implementations calculated to achieve the same
purposes may be substituted for the embodiments shown and described
without departing from the scope. Those with skill in the art will
readily appreciate that herein may be implemented in a very wide
variety of ways. This application is intended to cover any
adaptations or variations of the embodiments discussed herein.
Therefore, it is manifestly intended that embodiments be limited
only by the claims and the equivalents thereof.
* * * * *