U.S. patent application number 11/634195 was filed with the patent office on 2007-06-07 for fixed abrasive polishing pad, method of preparing the same, and chemical mechanical polishing apparatus including the same.
Invention is credited to Jae-ouk Choo, Ja-eung Koo, Se-young Lee, Hong-jae Shin, Il-young Yoon.
Application Number | 20070128991 11/634195 |
Document ID | / |
Family ID | 38119416 |
Filed Date | 2007-06-07 |
United States Patent
Application |
20070128991 |
Kind Code |
A1 |
Yoon; Il-young ; et
al. |
June 7, 2007 |
Fixed abrasive polishing pad, method of preparing the same, and
chemical mechanical polishing apparatus including the same
Abstract
A fixed abrasive polishing pad includes a base and a plurality
of polishing layers on the base, wherein each polishing layer
includes abrasive particles and apertures in a polishing surface of
the polishing layer.
Inventors: |
Yoon; Il-young;
(Hwaseong-si, KR) ; Shin; Hong-jae; (Seoul,
KR) ; Lee; Se-young; (Suwon-si, KR) ; Choo;
Jae-ouk; (Yongin-si, KR) ; Koo; Ja-eung;
(Suwon-si, KR) |
Correspondence
Address: |
LEE & MORSE, P.C.
3141 FAIRVIEW PARK DRIVE
SUITE 500
FALLS CHURCH
VA
22042
US
|
Family ID: |
38119416 |
Appl. No.: |
11/634195 |
Filed: |
December 6, 2006 |
Current U.S.
Class: |
451/56 ; 451/285;
451/548 |
Current CPC
Class: |
B24B 37/245 20130101;
B24B 37/26 20130101 |
Class at
Publication: |
451/056 ;
451/285; 451/548 |
International
Class: |
B24B 1/00 20060101
B24B001/00; B24B 29/00 20060101 B24B029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2005 |
KR |
10-2005-0119089 |
May 25, 2006 |
KR |
10-2006-0047120 |
Claims
1. A fixed abrasive polishing pad, comprising: a base; and a
plurality of polishing layers on the base, wherein each polishing
layer includes: abrasive particles, and apertures in a polishing
surface of the polishing layer.
2. The fixed abrasive polishing pad as claimed in claim 1, wherein
at least some of the apertures are interconnected within the
polishing layer.
3. The fixed abrasive polishing pad as claimed in claim 1, wherein
the apertures are formed using a foaming agent.
4. The fixed abrasive polishing pad as claimed in claim 1, wherein
the apertures have a predetermined pattern in the polishing
surface.
5. The fixed abrasive polishing pad as claimed in claim 4, wherein
the predetermined pattern is a mold pattern.
6. The fixed abrasive polishing pad as claimed in claim 4, wherein
the apertures are arranged at regular intervals.
7. The fixed abrasive polishing pad as claimed in claim 4, wherein
the apertures have a regular shape.
8. The fixed abrasive polishing pad as claimed in claim 1, wherein
the apertures occupy about 5-50% of the polishing surface of each
of the polishing layers.
9. The fixed abrasive polishing pad as claimed in claim 8, wherein
the apertures occupy about 5-30% of the polishing surface of each
of the polishing layers.
10. The fixed abrasive polishing pad as claimed in claim 1, wherein
the polishing pad includes: central polishing layers disposed in a
center region; and edge polishing layers disposed in an edge
region, wherein the apertures in the polishing surface of the
central polishing layers occupy a different area percentage of the
polishing surface than do the apertures in the polishing surface of
the edge polishing layers.
11. The fixed abrasive polishing pad as claimed in claim 10,
wherein the aperture area percentage in the central polishing
layers is greater than the aperture area percentage in the edge
polishing layers.
12. A method of manufacturing a fixed abrasive polishing pad, the
method comprising: forming a base; and disposing polishing layers
on the base, each of the polishing layers including apertures in a
polishing surface thereof and abrasive particles.
13. The method as claimed in claim 12, wherein the apertures occupy
about 5-50% of the polishing surface of each of the polishing
layers.
14. The method as claimed in claim 13, wherein the apertures occupy
about 5-30% of the polishing surface of each of the polishing
layers.
15. The method as claimed in claim 12, wherein the apertures are
formed by combining a foaming agent with a polymeric binder.
16. The method as claimed in claim 15, wherein forming the
polishing layers comprises: forming a mixture including the
polymeric binder and the foaming agent; forming apertures in the
mixture using the foaming agent; distributing abrasive particles in
the mixture; and forming the polishing layers by processing the
mixture including the distributed abrasive particles using a
printing process.
17. The method as claimed in claim 16, wherein the apertures are
formed by heating the foaming agent.
18. The method as claimed in claim 15, wherein the foaming agent
includes at least one of Na.sub.2SO.sub.4, NaHCO.sub.3, ADCA, OBSH,
and TSH.
19. The method as claimed in claim 12, wherein the apertures are
formed using a mold having a predetermined pattern therein, the
pattern corresponding to a pattern of apertures in the polishing
surface.
20. The method as claimed in claim 19, wherein forming the
apertures includes: distributing abrasive particles in a
UV-hardenable polymeric binder; molding the polishing layers using
the mold; and irradiating the molded polishing layers with UV
light.
21. The method as claimed in claim 19, wherein forming the
apertures includes: distributing abrasive particles in a
thermosetting polymeric binder; molding the polishing layers using
the mold; and heating the molded polishing layers.
22. The method as claimed in claim 19, wherein the mold includes a
fine pattern of projections on a molding surface, the projections
forming the apertures in the polishing surface.
23. A chemical mechanical polishing apparatus, comprising: a wafer
carrier; a fixed abrasive polishing pad including a base and
polishing layers disposed on the base; a slurry supplier; and a
supporter supporting the polishing pad, wherein each polishing
layer includes: abrasive particles, and apertures formed in a
polishing surface of the polishing layer.
24. The chemical mechanical polishing apparatus as claimed in claim
23, wherein the polishing layers are formed using a foaming
agent.
25. The chemical mechanical polishing apparatus as claimed in claim
23, wherein the apertures have a predetermined pattern in the
polishing surface.
26. The chemical mechanical polishing apparatus as claimed in claim
23, wherein the chemical mechanical polishing apparatus is rotary
type having a first roller for supplying the polishing pad, and a
second roller for receiving a portion of the polishing pad that has
performed a polishing process.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an apparatus for
manufacturing a semiconductor device. More particularly, the
present invention relates to a fixed abrasive polishing pad, a
method of preparing the same, and chemical mechanical polishing
(CMP) apparatus including the same.
[0003] 2. Description of the Related Art
[0004] CMP is a process for planarizing a surface of a substrate,
e.g., a semiconductor wafer, which may include a variety of
structures, films, etc. formed thereon. CMP effects planarization
by combining a mechanical polishing effect with a chemical reaction
effect. The mechanical polishing typically involves the application
of an abrasive to the wafer surface. The chemical reaction
typically involves the application of a reactant solution, e.g., an
acidic or basic solution, to the wafer. CMP is a planarization
process frequently employed for removing protrusions from a wafer
surface, and is very important to the manufacture of semiconductor
devices, particularly those having fine multi-layered wiring
structures.
[0005] A typical CMP apparatus may include a polishing head, which
rotates while pressing an elastic polishing pad against a wafer, a
pad conditioner for maintaining the polishing pad in a desired
state, and an apparatus for supplying a polishing slurry, i.e., a
polishing solution. In some applications, the slurry may include an
abrasive and/or a reactive solution, e.g., an acidic or basic
solution. When the wafer is pressed by the polishing pad while the
slurry is being supplied thereto, the acidic or basic solution
chemically reacts with the surface of the wafer while the surface
of the wafer is mechanically polished by the abrasive to reduce or
eliminate uneven surface features. In other applications, the CMP
apparatus may use a fixed abrasive polishing pad, in which an
abrasive is incorporated into the polishing pad. This CMP apparatus
may be used to planarize, e.g., a shallow trench isolation (STI)
film.
[0006] FIG. 1 illustrates photographically an upper surface of a
conventional fixed abrasive polishing pad, and FIGS. 2A and 2B are
magnified portions of a polishing layer of the polishing pad of
FIG. 1. Referring to FIG. 1, the fixed abrasive polishing pad has a
plurality of hexagonal polishing layers PL arranged thereon. The
polishing layers PL include abrasive particles. For example, ceria
(CeO.sub.2) particles may be used for CMP of an STI film.
[0007] Those skilled in the art of CMP will appreciate that there
is a high demand for polishing apparatuses capable of providing
uniformly planar and defect-free results across very large
surfaces. As illustrated in FIGS. 2A and 2B, the conventional CMP
fixed abrasive polishing pad utilizes polishing layers PL having
smooth surfaces that are free of lumps or holes.
[0008] FIG. 3 illustrates a graph of results of a polishing
operation performed using a chemical mechanical polishing (CMP)
apparatus including the conventional fixed abrasive polishing pad
of FIG. 1. In particular, the results were obtained by forming a
nitride film hard mask on a wafer, which was etched to a shallow
depth using the nitride film as an etch mask. An oxide film was
deposited on the etched wafer, thereby forming an STI oxide film.
Thereafter, the STI oxide film was subjected to CMP using the
polishing pad of FIG. 1.
[0009] Referring to FIG. 3, the etch rate RR of the STI oxide film
at the center of the wafer (0 on the x-axis) is significantly less
than the etch rate RR of the STI oxide film at the edges of the
wafer. As a result, the oxide film overlying the nitride film at
the center of the wafer is not effectively removed.
[0010] One approach to solving this problem is to apply more
pressure at the center of the wafer than at the edge. However, it
may be difficult to increase the contact pressure between the
polishing pad and the wafer only at the center of the wafer because
of the characteristics of the polishing pad, and thus the oxide
film etch rate may increase across the wafer. Besides being
difficult to apply more pressure to only the center of the wafer in
an actual practice, there is a risk that the wafer will be
scratched. In fact, the increased pressure may prevent the surface
of the layer being polishing from being chemically polished,
because the increased pressure may impede the delivery of slurry,
which contains the reactant solution, to the contact area between
the wafer and the polishing layers PL.
SUMMARY OF THE INVENTION
[0011] The present invention is therefore directed to a fixed
abrasive polishing pad, a method of preparing the same, and
chemical mechanical polishing apparatus including the same, which
substantially overcome one or more of the problems due to the
limitations and disadvantages of the related art.
[0012] It is therefore a feature of an embodiment of the present
invention to provide a polishing pad including a base having
polishing layers, the polishing layers having apertures.
[0013] It is therefore another feature of an embodiment of the
present invention to provide a polishing pad having polishing
layers with apertures formed therein, which may enhance the ability
of a slurry to infiltrate a contact area between the polishing
layers and a target substrate.
[0014] It is therefore yet another feature of an embodiment of the
present invention to provide a polishing pad having polishing
layers with apertures formed therein, where the area percentage of
apertures in central polishing pad layers is different from the
area percentage of apertures in edge polishing pad layers, such
that a CMP rate may be adjusted across the surface of the polishing
pad.
[0015] At least one of the above and other features and advantages
of the present invention may be realized by providing a fixed
abrasive polishing pad including a base and a plurality of
polishing layers on the base, wherein each polishing layer includes
abrasive particles and apertures in a polishing surface of the
polishing layer.
[0016] At least some of the apertures may be interconnected within
the polishing layer. The apertures may be formed using a foaming
agent. The apertures may have a predetermined pattern in the
polishing surface. The predetermined pattern may be a mold pattern.
The apertures may be arranged at regular intervals. The apertures
may have a regular shape. The apertures may occupy about 5-50% of
the polishing surface of each of the polishing layers. The
apertures may occupy about 5-30% of the polishing surface of each
of the polishing layers.
[0017] The polishing pad may include central polishing layers
disposed in a center region, and edge polishing layers disposed in
an edge region, wherein the apertures in the central polishing
layers may occupy a different area percentage of the polishing
surface than do the apertures in the edge polishing layers. The
aperture area percentage in the central polishing layers may be
greater than the aperture area percentage in the edge polishing
layers.
[0018] At least one of the above and other features and advantages
of the present invention may also be realized by providing a method
of manufacturing a fixed abrasive polishing pad, the method
including forming a base and disposing polishing layers on the
base, each of the polishing layers including apertures in a
polishing surface thereof and abrasive particles.
[0019] The apertures may occupy about 5-50% of the polishing
surface of each of the polishing layers. The apertures may occupy
about 5-30% of the polishing surface of each of the polishing
layers. The apertures may be formed by combining a foaming agent
with a polymeric binder. Forming the polishing layers may include
forming a mixture including the polymeric binder and the foaming
agent, forming apertures in the mixture using the foaming agent,
distributing abrasive particles in the mixture, and forming the
polishing layers by processing the mixture including the
distributed abrasive particles using a printing process. The
apertures may be formed by heating the foaming agent. The foaming
agent may include at least one of Na.sub.2SO.sub.4, NaHCO.sub.3,
ADCA, OBSH, and TSH.
[0020] The apertures may be formed using a mold having a
predetermined pattern therein, the pattern corresponding to a
pattern of apertures in the polishing surface. Forming the
apertures may include distributing abrasive particles in a
UV-hardenable polymeric binder, molding the polishing layers using
the mold, and irradiating the molded polishing layers with UV
light. Forming the apertures may include distributing abrasive
particles in a thermosetting polymeric binder, molding the
polishing layers using the mold, and heating the molded polishing
layers. The mold may include a fine pattern of projections on a
molding surface, the projections forming the apertures in the
polishing surface.
[0021] At least one of the above and other features and advantages
of the present invention may further be realized by providing a
chemical mechanical polishing apparatus, including a wafer carrier,
a fixed abrasive polishing pad including a base and polishing
layers disposed on the base, a slurry supplier, and a supporter
supporting the polishing pad, wherein each polishing layer includes
abrasive particles, and apertures formed in a polishing surface of
the polishing layer.
[0022] The polishing layers may be formed using a foaming agent.
The apertures may have a predetermined pattern in the polishing
surface. The chemical mechanical polishing apparatus may be rotary
type having a first roller for supplying the polishing pad, and a
second roller for receiving a portion of the polishing pad that has
performed a polishing process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other features and advantages of the present
invention will become more apparent to those of ordinary skill in
the art by describing in detail exemplary embodiments thereof with
reference to the attached drawings, in which:
[0024] FIG. 1 photographically illustrates an upper surface of a
conventional fixed abrasive polishing pad;
[0025] FIGS. 2A and 2B are magnified portions of a polishing layer
of the polishing pad of FIG. 1;
[0026] FIG. 3 illustrates a graph of results of a polishing
operation performed using a chemical mechanical polishing (CMP)
apparatus including the conventional fixed abrasive polishing pad
of FIG. 1;
[0027] FIG. 4 illustrates a perspective view of a fixed abrasive
polishing pad according to an embodiment of the present
invention;
[0028] FIG. 5 illustrates a cross-section of a polishing layer of
the polishing pad of FIG. 4;
[0029] FIG. 6 illustrates a perspective view of a fixed abrasive
polishing pad according to another embodiment of the present
invention;
[0030] FIG. 7 illustrates a cross-section of a polishing layer of
the polishing pad of FIG. 6; and
[0031] FIG. 8 illustrates a schematic view of a CMP apparatus
including a fixed abrasive polishing pad according to an embodiment
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] Korean Patent Application Nos. 10-2005-0119089 and
10-2006-0047120, filed on Dec. 7, 2005, and May 25, 2006,
respectively, in the Korean Intellectual Property Office, both of
which are entitled "Fixed Abrasive Polishing Pad, Method of
Preparing the Same, and Chemical Mechanical Polishing Apparatus
Including the Same," are incorporated by reference herein in their
entirety.
[0033] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the invention are illustrated. The
invention may, however, be embodied in different forms and should
not be construed as limited to the embodiments set forth herein.
Rather, these embodiments are provided so that this disclosure will
be thorough and complete, and will fully convey the scope of the
invention to those skilled in the art.
[0034] In the figures, the dimensions of layers and regions may be
exaggerated for clarity of illustration. It will also be understood
that when a layer or element is referred to as being "on" another
layer or substrate, it can be directly on the other layer or
substrate, or intervening layers may also be present. Further, it
will be understood that when a layer is referred to as being
"under" another layer, it can be directly under, and one or more
intervening layers may also be present. In addition, it will also
be understood that when a layer is referred to as being "between"
two layers, it can be the only layer between the two layers, or one
or more intervening layers may also be present. Like reference
numerals refer to like elements throughout.
[0035] Embodiments of the present invention are directed to a fixed
abrasive polishing pad which may include apertures and abrasive
particles, and which may minimize damage to a target wafer while
evenly polishing the entire surface of the wafer during CMP, and a
method of making the same. An embodiment of the present invention
is also directed to a CMP apparatus which may evenly polish the
entire surface of the target wafer, which may enhance productivity
and which may improve reliability of a semiconductor device made
therewith.
[0036] The apertures or recesses in the polishing pad may allow a
slurry to exist in contact areas between the wafer and each of the
polishing layers, so that both mechanical polishing by abrasive
particles and chemical polishing by a reactive agent in the slurry
may be effected. In particular, spaces may be formed in the contact
areas due to the apertures, which may allow slurry to be contained
in the spaces. Thus, a chemical reaction between the slurry and the
wafer may be effected. In addition, since abrasive particles
included in the polishing layers may be easily carried out by the
slurry, mechanical polishing may also be effected. Therefore, the
use of a polishing pad according to the present invention may allow
the entire surface of the wafer to be evenly
chemically-mechanically polished. The CMP apparatus may include a
rotary-type polishing pad, so that continuous CMP processes may be
conducted without need to frequently replace the polishing pad as
the polishing layers are consumed.
[0037] FIG. 4 illustrates a perspective view of a fixed abrasive
polishing pad according to an embodiment of the present invention,
and FIG. 5 illustrates a cross-section of a polishing layer of the
polishing pad of FIG. 4. Referring to FIGS. 4 and 5, a fixed
abrasive polishing pad 30 may include a plurality of polishing
layers 31 arranged on a base 32, the polishing layers 31 including
abrasive particles 36 and apertures 38.
[0038] The base 32 may include a polymer exhibiting suitable
strength, elasticity and durability. When the fixed abrasive
polishing pad 30 is a rotary type pad, the base 32 should have
enough elasticity to maintain sufficient tension to prevent the
base 32 from loosening.
[0039] The base 32 may be a single layer. Alternatively, since it
may be desirable for the base 32 to exhibit characteristics such as
strength, elasticity, and durability, the base 32 may be a
multi-layer structure obtained by stacking materials exhibiting the
aforementioned characteristics. For example, a rotary-type
polishing pad may have a base 32 made up of a flexible underlayer
and a hard upper layer that is disposed on the flexible underlayer,
so that the performance of the polishing pad increases while the
polishing pad is also flexible enough to be bent around
rollers.
[0040] The base 32 may be formed of, e.g., polyurethane, polyester,
polyether, epoxy, polyimide, polycarbonate, polyethylene,
polypropylene, latex, nitrile rubber, isoprene rubber, or any other
suitable material. Polyurethane may be a particularly suitable
material for the base 32.
[0041] The polishing layers 31 may be formed on the base 32 after
forming the base 32. The polishing layers 31 may include the
abrasive particles 36 distributed in a polymer 34. As the polymer
34 may be gradually reduced during the CMP process by the action of
the slurry, the abrasive particles 36 contained in the polymer 34
may be exposed and rub against the target wafer.
[0042] The polymer 34 may allow the abrasive particles 36 therein
to be gradually exposed by the polishing action of the slurry, so
as to abrade the target wafer. The polymer 34 may be formed using
polymeric binders, e.g., thermoplastic materials, thermosetting
materials, ultraviolet (UV) hardenable materials, etc. The polymer
34 may be, e.g., polyurethane, polypropylene, polyacryl,
polyethylene, a block co-polymer, etc. The polymer 34 may be formed
of, e.g., a mixture of an active hydrogen compound used to form
polyurethane and an isocyanate as a polymerization catalyst. The
polymer 34 may be sintered or hardened by heat or UV light and
fixed onto the base 32.
[0043] The abrasive particles 36 may be distributed in the polymer
34 to thereby form the polishing layers 31. The abrasive particles
36 may be, e.g., silica (SiO.sub.2), ceria (CeO.sub.2), alumina
(Al.sub.2O.sub.3), etc. In a CMP process for an STI oxide film,
ceria may be particularly suitable for the abrasive particles
36.
[0044] The polishing layers 31 may have various shapes and sizes,
which may be determined according to, e.g., the target wafer to be
polished, the bonding agents, the nature of the abrasive particles,
the polishing process conditions, etc. Where the pad 30 is used in
a CMP process for an STI oxide film, each of the polishing layers
31 may have a width of about 50-200 .mu.m and a thickness of about
20-50 .mu.m.
[0045] The polishing layers 31 may include various additives
suitable for enhancing the CMP process. The additives may include,
e.g., one or more of a viscosity modifier, a wetting agent, etc.
The viscosity modifier may be employed to enhance the lubrication
property of the polishing layers 31 when the polishing layers 31
contact the wafer, so that the abrasive particles or the additives
spread evenly over areas of the wafer that contact the polishing
layers 31. Hence, the viscosity modifier may enhance the CMP
planarization. The viscosity modifier may include, e.g., ethylene
glycol or a nonionic polymer compound, such as a gum compound. The
wetting agent may be employed to improve the miscibility and
dispersiveness of the abrasive particles 36 across the polymer
34.
[0046] Referring to FIG. 5, slurry may reside in the apertures 38
during CMP. Hence, a chemical reaction between the slurry and the
wafer may occur in the contact between the polishing layers 31 and
the wafer, even in consideration of a predetermined pressure that
may be applied to the pad 30 in order to accelerate polishing. The
slurry may include various materials suitable for the object to be
polished. For example, for CMP of a wafer 20 having an STI oxide
film formed thereon, the slurry may include, e.g., one or more of
an oxidizing agent, an etch solution, and a surface active
agent.
[0047] The apertures 38 may be formed in the polymer 34. The
apertures 38 may have various shapes, and may be formed by various
methods. The apertures 38 may or may not be interconnected within
each polishing layer 31. The area of the apertures 38 may occupy
about 5-50% of the area of each of the polishing layers 31. In an
implementation, the area of the apertures 38 may occupy about 5-30%
of the area of each of the polishing layers 31. If a small number
of apertures 38 are formed in each polishing layer 31, the amount
of slurry contained in the apertures 38 may be low, and the
chemical polishing process may not be efficient. If a large number
of apertures 38 are formed in each polishing layer 31, the amount
of abrasive particles 39 contained in the polymer 34 of each
polishing layer 31 may be reduced, and the mechanical polishing
process may not be efficient.
[0048] In an implementation, the percentage of each polishing layer
31 occupied by the apertures 38 may be substantially uniform. In
another implementation, the percentages of the polishing layers 31
occupied by the apertures 38 may be different across the pad 30, in
order to control polishing rates on different areas on the wafer.
For example, if the polishing and removal rate tends to be lower at
the center of the target wafer than that of the edge, a greater
number of apertures 38 may be formed in those polishing layers 31
that are located at the center of the pad 30, relative to the
number of apertures formed in those polishing layers 31 that are
located on the edge of the pad 30.
[0049] The apertures 38 may be formed by combining a foaming agent
with a polymeric binder during formation of the polishing layers
31. The foaming agent may be an inorganic foaming agent such as
Na.sub.2SO.sub.4, NaHCO.sub.3, etc., or an organic foaming agent
such as azocarbonamide (ADCA), OBSH
(p,p'-oxybis(benzenesulfonylhydrazide)), TSH
(p-tolunesulfonylhydrazide), etc. The amount of the foaming agent
used may vary according to the size, polishing speed, or other
desired characteristics of the polishing layers 31.
[0050] The apertures 38 may be, e.g., pores, and may be formed by
injecting the foaming agent into a polymeric binder so as to form a
mixture, and then apertures may be formed in the mixture by using a
foaming machine or by heating the mixture. Thereafter, the mixture
may be poured into a previously manufactured mold and hardened,
e.g., using UV light or heat, to thereby form the polishing layers
31. The polishing layers 31 may be attached to the base 32 to make
the polishing pad 30.
[0051] Different amounts of foaming agent may be used in those
polishing layers 31 that correspond to the center of the wafer as
compared to those corresponding to the edge of the wafer. That is,
if the polishing rate at the center of the wafer is less than that
at the edge thereof, the polishing rate at the center of the wafer
may be increased by using a greater amount of the foaming agent in
the polishing layers 31 that are disposed in the center of the
polishing pad 30 than in those corresponding to the edge of the
wafer.
[0052] FIG. 6 illustrates a perspective view of a fixed abrasive
polishing pad according to another embodiment of the present
invention, and FIG. 7 illustrates a cross-section of a polishing
layer of the polishing pad of FIG. 6. Referring to FIG. 6, a fixed
abrasive polishing pad 30' may include the base 32 and polishing
layers 33. The polishing layers 33 may include the abrasive
particles 36 and the polymer 34, as described above in connection
with FIG. 4. Referring to FIGS. 6 and 7, the polishing layers 33
may include apertures 39 that have predetermined forms and a
regular arrangement or pattern.
[0053] The apertures 39 may be formed using, e.g., a mold having a
fine concave/convex structure. The abrasive particles 36 may be
distributed in a polymeric binder so as to form a mixture, which
may then be poured into a mold corresponding to each the polishing
layers 33 having the apertures 39. UV light, heat, etc., may be
applied to the mixture in order to harden the polymer 34, to
thereby form the polishing layers 33. The polishing layers 33 may
be attached to the base 32 to form the pad 30' of FIG. 6.
[0054] Apertures 39, in the form of, e.g., recesses or grooves, may
be formed in the polishing layers 33. The apertures 39 may be
formed using a mold having a fine structure of an inverse pattern,
e.g., a concave/convex structure. The mold may include a fine
pattern of projections on a molding surface, so that, during
molding, the projections form the apertures 39 in the polishing
surface of the polishing layers 33. The mold used for those
polishing layers 33 that correspond to the center of the wafer may
be different from the mold used for those polishing layers 33 that
correspond to the edge of the wafer. If the polishing rate at the
center of the wafer is less than that at the edge thereof, the
polishing rate at the center of the wafer may be increased by using
mold that forms a predetermined pattern having a greater amount of
aperture area for the polishing layers 33 that are disposed in the
center of the polishing pad 30, and using a mold that forms a
different predetermined pattern having a lesser amount of aperture
area for the polishing layers 33 that correspond to the edge of the
wafer.
[0055] The shape of the apertures 39 may be suitably varied by
varying to the shapes of the concave and/or convex structures in
the mold. The apertures 39 may be, e.g., tetrahedral, hexahedral,
etc. The depth of the apertures 39 may be less than the thickness
of the polishing layer 33, such that the apertures 39 do not
completely penetrate through the polishing layer 33. The area of
the apertures 39 may occupy about 5-50% of the area of each of the
polishing layers 33. In an implementation, the area of the
apertures 39 may occupy about 5-30% of the area of each of the
polishing layers 33.
[0056] For a UV-hardenable polymer 34, the polymer 34, into which
abrasive particles 36 may be evenly dispersed, may be partially or
completely hardened by UV light projected onto the polymer 34, and
then molded using the mold, thereby forming the apertures 39
corresponding to the fine concave/convex structure of the mold.
Similarly, apertures 39 may be formed in a thermosetting polymer 34
by molding the polymer 34 using the mold after heating the polymer
34.
[0057] Referring to FIG. 7, the abrasive particles 36 and the
apertures 39 may be evenly distributed in the polymer 34. By using
a mold having regular features, the apertures 39 may be arranged at
regular intervals. In an implementation, the apertures 39 formed in
each of the polishing. layers 33 may have the same shapes and area
percentages, in order to equalize the amount of slurry contained in
each the polishing layers 33 across all of the polishing layers 33.
This may enhance the uniformity of the chemical reactions occurring
during wafer polishing. Alternatively, as described above, the
polishing pad may be formed with differing aperture area ratios
for, e.g., the center and edge polishing layers 33. In particular,
the approaches described above in connection with FIGS. 4 and 6 may
be employed.
[0058] The fixed abrasive polishing pads 30, 30' described above
may be, e.g., flat, circular type or a rotary type pads. FIG. 8
illustrates a schematic view of a CMP apparatus including a fixed
abrasive polishing pad according to an embodiment of the present
invention. The CMP apparatus of FIG. 8 is a rotary-type CMP
apparatus, and the polishing pad illustrated in FIG. 8 may be,
e.g., the polishing pad 30 of FIG. 4. Of course, the polishing pad
employed may be, e.g., the pad 30' having the polishing layers 33
formed thereon (not shown). Referring to FIG. 8, the CMP apparatus
may include the polishing pad 30, wherein the polishing layers 31,
including abrasive particles 36 and apertures 38, are formed on the
base 32.
[0059] The polishing layers 31 may be formed to have a width of
about 50-200 .mu.m and a thickness of about 20-50 .mu.m. Note that,
in FIG. 8, the polishing layers 31 are illustrated with exaggerated
dimensions for clarity.
[0060] The polishing pad 30 may be initially wound around a first
roller 50. The polishing pad 30 may be unwound from the first
roller 50 and travel on a supporter 40, e.g., a platen. A wafer 20
may be carried by a wafer carrier 10 to be located over the
polishing pad 30. When the wafer carrier 20 descends, a layer of
the target wafer 20 may be chemically-mechanically polished by
rubbing against the polishing layers 31 of the polishing pad
30.
[0061] The CMP apparatus may further include a second roller 52 for
winding up the polishing pad 30 as it is consumed. After use, the
polishing pad 30 may be discarded. A slurry provider 60 may be
employed to provide a slurry over the polishing pad 30.
[0062] The polymer 34 of the polishing layers 31 may be worn away
by the slurry, allowing the abrasive particles 36 to rub against
and abrade the to-be-polished layer of the wafer 20, whereby the
wafer 20 is mechanically polished. The apertures 38 formed in the
polishing layers 31 may contain the slurry, and the contained
slurry and the to-be-polished layer of the wafer 20 may react with
each other, whereby the wafer 20 is chemically polished. The
chemical and mechanical action of the CMP process may continuously
expose additional abrasive particles 36 in the polymer 34 that
forms the polishing layers 31. Since the slurry can permeate into
the contact between the polishing pad 30 and the wafer 20 due to
presence of the apertures 38, chemical polishing may be enhanced.
Furthermore, since the abrasive particles 36 at the center of the
contact may be exposed and released by flow of the slurry contained
in the apertures 38 from the central portion of the contact,
mechanical polishing may be even across the surface of the
to-be-polished layer of the wafer 20.
[0063] As described above, in a fixed abrasive polishing pad
according to the present invention, polishing layers having
apertures and disposed on a base, so that a slurry can be contained
in the apertures near the contact between the polishing layers and
a to-be-polished layer of a wafer. The slurry contained in the
apertures may thus react with the to-be-polished layer, so that
chemical polishing is effected. Simultaneously, abrasive particles
in the polishing layers exposed and released by the slurry may
abrade the wafer 20, so that mechanical polishing is effected. By
utilizing the fixed abrasive polishing pad according to the present
invention in a CMP process, the to-be-polished layer may be evenly
polished, and the reliability and productivity of a semiconductor
device manufactured thereby may be improved.
[0064] Exemplary embodiments of the present invention have been
disclosed herein, and although specific terms are employed, they
are used and are to be interpreted in a generic and descriptive
sense only and not for purpose of limitation. Accordingly, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made without departing from the
spirit and scope of the present invention as set forth in the
following claims.
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