U.S. patent application number 10/973827 was filed with the patent office on 2005-05-26 for post cmp scrubbing of substrates.
This patent application is currently assigned to APPLIED MATERIALS, INC.. Invention is credited to Huey, Sidney P., Ko, Terry Kin-Ting, Sin, Garrett H..
Application Number | 20050109371 10/973827 |
Document ID | / |
Family ID | 34594807 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050109371 |
Kind Code |
A1 |
Sin, Garrett H. ; et
al. |
May 26, 2005 |
Post CMP scrubbing of substrates
Abstract
A cleaning apparatus is provided for brush cleaning a surface of
a substrate. The apparatus comprises a first brush having a first
surface geometry adapted to scrub a major surface of the substrate,
and a second brush having a second surface geometry different from
the first surface geometry and adapted to scrub the major surface
of the substrate. In one aspect the cleaning apparatus comprises a
first scrubbing apparatus having at least one brush with a profiled
surface geometry, adapted to scrub a major surface of a substrate,
and a second scrubbing apparatus having at least one brush with a
smooth surface geometry, adapted to scrub a major surface of a
substrate. Numerous other aspects are provided.
Inventors: |
Sin, Garrett H.; (San Jose,
CA) ; Ko, Terry Kin-Ting; (Millbrae, CA) ;
Huey, Sidney P.; (Milpitas, CA) |
Correspondence
Address: |
DUGAN & DUGAN, PC
55 SOUTH BROADWAY
TARRYTOWN
NY
10591
US
|
Assignee: |
APPLIED MATERIALS, INC.
|
Family ID: |
34594807 |
Appl. No.: |
10/973827 |
Filed: |
October 26, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60514708 |
Oct 27, 2003 |
|
|
|
Current U.S.
Class: |
134/6 ; 15/77;
15/88.3 |
Current CPC
Class: |
B08B 3/02 20130101; H01L
21/67046 20130101; B08B 1/002 20130101; B08B 1/04 20130101 |
Class at
Publication: |
134/006 ;
015/077; 015/088.3 |
International
Class: |
B08B 001/04 |
Claims
The invention claimed is:
1. A cleaning apparatus for brush cleaning a surface of a
substrate, comprising: a first brush having a first surface
geometry adapted to scrub a major surface of the substrate; and a
second brush having a second surface geometry different from the
first surface geometry and adapted to scrub the major surface of
the substrate.
2. The apparatus of claim 1, wherein the first surface geometry is
profiled and the second surface geometry is smooth.
3. The apparatus of claim 1, wherein the first surface geometry is
smooth, and the second surface geometry is profiled.
4. The apparatus of claim 1, wherein the cleaning apparatus is
adapted such that the first brush and the second brush are
positioned for sequential application to a substrate.
5. The apparatus of claim 1, wherein one of the first brush and the
second brush comprises a plurality of raised nodules and the other
of the first and the second brush has a smooth surface.
6. The apparatus of claim 1, further comprising a controller
adapted to cause delivery of a first fluid to the first brush, and
a second fluid to the second brush.
7. A cleaning apparatus comprising: a first scrubbing apparatus
having at least one brush with a profiled surface geometry, adapted
to scrub a major surface of a substrate; and a second scrubbing
apparatus having at least one brush with a smooth surface geometry,
adapted to scrub a major surface of a substrate.
8. The cleaning apparatus of claim 7, wherein the at least one
brush of the first scrubbing apparatus is a roller brush, and
wherein the at least one brush of the second scrubbing apparatus is
a roller brush.
9. The cleaning apparatus of claim 8, wherein the profiled surface
geometry comprises nodules.
10. The cleaning apparatus of claim 9, wherein the first and the
second scrubbing apparatuses are each adapted to scrub the first
major surface of a substrate and a second major surface of the
substrate simultaneously.
11. The cleaning apparatus of claim 10, wherein the first and the
second scrubbing apparatuses are each adapted to scrub a vertically
oriented substrate.
12. A method of cleaning a substrate comprising: scrubbing a first
surface of the substrate with a brush having a first surface
geometry; and then scrubbing the first surface of the substrate
with a brush having a second surface geometry, wherein the first
and the second surface geometries are different.
13. The method of claim 12, wherein the first surface geometry is
profiled and the second surface geometry is smooth.
14. The method of claim 12, wherein the first surface geometry is
smooth and the second surface geometry is profiled.
15. The method of claim 13, wherein scrubbing with the brush having
the smooth surface geometry comprises trapping a cleaning fluid
between the first surface of the substrate and the brush having the
smooth surface geometry.
16. The method of claim 12, wherein a first cleaning fluid is
applied while scrubbing with the brush having the first surface
geometry, and a second cleaning fluid is applied while scrubbing
with the brush having the second surface geometry.
17. The method of claim 12, wherein a first concentration of a
first cleaning fluid is applied while scrubbing with the brush
having the first surface geometry and a second concentration of the
first cleaning fluid is applied while scrubbing with the brush
having the second surface geometry.
Description
[0001] The present application claims priority from U.S.
Provisional Patent Application Ser. No. 60/514,708, filed Oct. 27,
2003, which is hereby incorporated by reference herein in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to systems for
fabricating semiconductor devices, and is more particularly related
to methods and apparatus for cleaning substrates.
BACKGROUND OF THE INVENTION
[0003] For fabrication of semiconductor devices, substrates such as
thin slices or wafers of semiconductor material require polishing
by a process that applies an abrasive slurry to a substrate's
surfaces. After polishing, slurry residue is generally cleaned or
scrubbed from substrate surfaces via mechanical scrubbing devices,
such as polyvinyl acetate (PVA) brushes, brushes made from other
porous or sponge-like material, or brushes made with nylon
bristles.
[0004] Using conventional scrubbing techniques, an undesirable
number of particles may remain on scrubbed substrate surfaces.
Accordingly, a need exists for improved methods and apparatus for
scrubbing substrates.
SUMMARY OF THE INVENTION
[0005] An inventive cleaning apparatus is provided for brush
cleaning a surface of a substrate. The apparatus comprises a first
brush having a first surface geometry adapted to scrub a major
surface of the substrate, and a second brush having a second
surface geometry different from the first surface geometry and
adapted to scrub the major surface of the substrate.
[0006] In one aspect the cleaning apparatus comprises a first
scrubbing apparatus having at least one brush with a profiled
surface geometry, adapted to scrub a major surface of a substrate,
and a second scrubbing apparatus having at least one brush with a
smooth surface geometry, adapted to scrub a major surface of a
substrate.
[0007] Also provided is an inventive method of cleaning a
substrate. The inventive method comprises scrubbing a first surface
of the substrate with a brush having a first surface geometry, and
then scrubbing the first surface of the substrate with a brush
having a second surface geometry. In this aspect the first and the
second surface geometries also differ from each other.
[0008] Other features and aspects of the present invention will
become more fully apparent from the following detailed description,
the appended claims and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a partially schematic illustration of an inventive
substrate cleaning system for cleaning a substrate in accordance
with the present invention.
[0010] FIG. 2A is a side, cross-sectional view of an exemplary
nodular surface geometry that may be employed with the substrate
cleaning system of FIG. 1.
[0011] FIG. 2B is a side, cross-sectional view of an exemplary
smooth surface geometry that may be employed with the substrate
cleaning system of FIG. 1.
[0012] FIG. 3 illustrates a process for brush cleaning a surface of
a substrate in accordance with the present invention.
DETAILED DESCRIPTION
[0013] In an embodiment, the present invention includes a method of
cleaning a substrate including scrubbing a major surface of a
substrate with brushes of different (i.e., dissimilar) surface
geometries. In some such embodiments, at least two brushes having
different surface geometries are employed, one such brush having a
profiled (e.g., nodular) surface geometry, and another such brush
having a smooth surface geometry. In a first aspect, the major
surface of the substrate is initially scrubbed with the brush of
the nodular geometry, and is subsequently scrubbed with the brush
of the smooth geometry. In a second aspect, the above order is
reversed. In a further aspect, a lower concentration of cleaning
chemistry is employed when scrubbing with a profiled brush, and a
higher concentration employed when scrubbing with a smooth brush.
Effective cleaning of a substrate's surface via scrubbing with
brushes of different surface geometries may be advantageously
performed after CMP processing of the substrate surface.
[0014] The present inventors have discovered that scrubbing a
substrate with brushes of different surface geometries results in
fewer particles remaining on the scrubbed surface as compared to
the common practice in which no difference or gradient exists in
the surface geometries of the brushes used to scrub a particular
surface. While not intending to be bound by any particular theory,
it is believed that better post CMP cleaning may be a result of a
synergy involving different types of cleaning actions. For example,
a brush having a profiled surface geometry (i.e., having raised
surface features such as nodules) may contribute a stronger
mechanical cleaning action, whereas a brush having a smooth surface
geometry (e.g., a surface which includes no raised surface features
or bristles) may contribute a proportionately stronger chemical
cleaning action. It will be understood that chemical cleaning
action includes reduction in adhesion of particles to the substrate
surface. It further will be understood that surface geometry refers
to brush surface profile rather than to a pore size of brush
material.
[0015] Embodiments of the current invention include a substrate
cleaning system that includes a pair of scrubbing apparatuses
having scrubber brushes of different surface geometries.
Specifically in the exemplary embodiment partially schematically
illustrated in FIG. 1, an inventive substrate cleaning system 101
for cleaning a substrate S1 includes a first scrubbing apparatus
103 which employs at least one brush 105 having a nodular surface
geometry (e.g., such as is discussed in more detail below with
regard to FIG. 2A), and a second scrubbing apparatus 107 which
employs at least one brush 109 having a smooth surface geometry
(e.g., such as is discussed in more detail below with regard to
FIG. 2B). The brushes of the scrubbing apparatuses of FIG. 1 may,
for example, be porous and/or sponge like, and/or may be comprised
of a resilient material such as polyvinyl acetate (PVA). The
brushes may comprise other and/or different materials, and may
exhibit other and/or different material characteristics, provided
that a difference in surface geometry between brushes is present.
Note also that the brushes may be supported via any known support
mechanism or mechanisms (not shown) and maybe enclosed within a
chamber (not shown).
[0016] Each of the exemplary scrubbing apparatuses shown in FIG. 1
may be employed to scrub a vertically oriented substrate (such as
the substrate S1), and may comprise a pair of brushes so as to
permit scrubbing (e.g., simultaneous scrubbing) of both major
surfaces of the substrate S1, as well as rollers 111 for supporting
and rotating the substrate S1. Other numbers of brushes may be
used, and other substrate orientations are possible, such as a
horizontal orientation, or an inclined orientation. The brushes
105, 109 are adapted to contact at least one of the same major
surfaces of the substrate S1, for cleaning and/or removing slurry
residue and/or other particulates/contaminants therefrom.
[0017] The inventive substrate cleaning system 101 may further
include a first fluid delivery unit 113 for delivering fluid to the
first scrubbing apparatus 103, and a second fluid delivery unit 115
for delivering fluid to the second scrubbing apparatus 107.
(Alternatively, the same fluid delivery unit may deliver fluid to
both scrubbing apparatuses.) Whether one or two fluid delivery
units are employed, the same fluids may be delivered to both the
scrubbing apparatuses, or different fluids may be delivered. In
cases in which the same fluid is delivered to each scrubbing
apparatus, the same chemical concentration or a different chemical
concentration of the fluid may be delivered to each scrubbing
apparatus. In an embodiment, a solution of NH.sub.4OH at a
concentration of approximately 0.05% is delivered to the first
scrubbing apparatus 103, and a solution of NH.sub.4OH at a
concentration of approximately 1.0% is delivered to the second
scrubbing apparatus 107. Greater or lesser concentrations of
NH.sub.4OH may be used in either or both scrubbing apparatuses.
Different types of chemicals may also and/or alternatively be used.
The chemicals may, for example, be delivered in liquid form, and
may aid the scrubbing process by washing slurry residue and/or
other particulates/contaminants from brush and/or substrate
surfaces, by facilitating dislodgement of particles/contaminants
from substrate surfaces, and/or by dissolving or reducing adhesion
of (e.g., via chemical reaction) particulates/contaminants disposed
on brush and substrate surfaces.
[0018] As also shown in FIG. 1, each scrubbing apparatus may
include one or more spray bars 117 to which the fluid delivery unit
may deliver fluid. For example, the spray bar 117 may be located
adjacent and to one side of the substrate S1, and may be used to
direct a spray of fluid toward a first major surface of the
substrate S1. Other methods of applying fluid to the surface of the
substrate S1 and/or to the brushes may be used. In a particular
embodiment, chemicals are delivered to each of the scrubbing
apparatuses, and are sprayed on at least one major surface of the
substrate S1 by the spray bars 117 while the substrate S1 is
rotated at 50 RPM by the rollers 111.
[0019] In a particular embodiment, DI water is sprayed on at least
one major surface of the substrate S1 for 30 seconds in order to
rinse the substrate S1 after scrubbing of the major surface by the
profiled brushes 105 of the first scrubbing apparatus 103, and is
sprayed on the same major surface(s) of the substrate S1 for 20
seconds in order to rinse the substrate S1 after scrubbing of the
major surface by the smooth brushes 109 of the second scrubbing
apparatus 107.
[0020] The inventive substrate cleaning system 101 may further
include a first drive device 119 which may be employed to rotate
one or more of the brushes 105 of the first scrubbing apparatus
103, and a second drive device 121 which may be employed to rotate
one or more of the brushes 109 of the second scrubbing apparatus
107. Alternatively, the same drive device may be employed to rotate
one or more of the brushes of both scrubbing apparatuses. In a
particular embodiment, each brush is closed against the
corresponding major surface of the substrate S1, and is rotated at
400 RPM so as to scrub the substrate S1. It has been found that
scrubbing with the profiled brushes 105 for ten seconds, and
scrubbing with the smooth brushes 109 for twenty seconds provides
good particle removal.
[0021] The inventive substrate cleaning system 101 may further
include a controller 123 coupled to the first and second chemical
delivery units 113, 115 and/or to the first and second drive
devices 119, 121, and may be adapted to control the operation of
the same. For example, the controller 123 may comprise a
microprocessor, and the microprocessor may be programmed to
activate and/or control the chemical delivery units so as to
deliver chemicals to the scrubbing apparatuses at predetermined
times and/or rates, and/or for a predetermined length of time.
Similarly, the microprocessor of the controller 123 may be
programmed to activate and/or control the drive devices so as to
rotate the brushes at predetermined times and/or rates, and/or for
a predetermined length of time. The microprocessor of the
controller 123 may exert similar control over the delivery of DI
water, and/or over the rotation of the substrate S1 by one or more
of the rollers 11.
[0022] Without intending to be bound by theory, the present
inventors observe that many important differences in the capacity
of scrubber brushes to deliver different types and/or varying
degrees of mechanical and/or cleaning actions can be attributed to
surface geometry differences. For example, whether a brush is
adapted to deliver shear forces of various sizes and directions
beneficial for dislodging and wiping away surface particles
otherwise resistant to removal via chemical action, or to provide a
continuous region of brush/surface contact beneficial for trapping
or otherwise maintaining fluid therebetween so as to dissolve and
or reduce adhesion of surface particles which may otherwise be
resistant to removal via mechanical scrubbing, would appear to be
determined at least in part based on surface geometry.
[0023] The brushes illustrated in FIGS. 2A and 2B have different
surface geometries. For example, as between the exemplary
embodiment of a profiled brush 105 shown in the end view of FIG.
2A, and the exemplary embodiment of a smooth brush 109 shown in the
end view of FIG. 2B, profiled brush 105 may be considered to have a
relatively rough surface geometry, and smooth brush 109 may be
considered to have a relatively smooth surface geometry.
[0024] The profiled brush 105 of FIG. 2A features a plurality of
raised regions or nodules extending radially outward. In a
particular embodiment of the brush 105 of FIG. 2A, the brush
surface effectively comprises an inner surface 125 described by a
diameter 127, and an outer surface 129 described by a diameter 131,
the outer surface 129 essentially comprising a collection of
respective outward facing surfaces of a plurality of nodules 133
extending from the inner surface 125. The nodules of the particular
embodiment have a height 135 and a width 137, and are separated by
a peripheral spacing distance 139. Examples of suitable profiled
brushes that may be employed include Rippey Symmetry nodule
brushes, Texwipe Hydrocell nodule brushes, or the like. Other
dimensions and/or configurations for a particular profiled brush
105, such as a combination of different sized nodules, are
possible. The brush 105, being equipped with nodules such as the
nodules 133, has been observed to provide good mechanical cleaning
action when the brush 105 is rotated against major surfaces of the
substrate S1 in the presence of cleaning chemicals, e.g., resulting
in the dislodgement of particles that tend to resist removal via
chemical cleaning action.
[0025] The smooth brush 109 of FIG. 2B features no such raised
regions or nodules. In a particular embodiment of the smooth brush
109 of FIG. 2A, the brush surface essentially comprises a surface
141, which in one embodiment is described by a diameter 143, and is
characterized in that it may or may not comprise numerous surface
pores, but is also otherwise essentially peripherally and
longitudinally (i.e., in a direction passing normally into the
paper of FIG. 2A) continuous (i.e., the surface 141 features no
nodes, bristles, or other similar raised features of a large enough
size such as may amount to differences in surface geometry as the
term is used herein). Examples of suitable smooth brushes that may
be employed include Rippey Symmetry smooth brushes, Texwipe
Hydrocell smooth brushes, or the like. The smooth brush 109 of FIG.
2B, being free of nodes and/or other discontinuities which may, for
example, tend to prevent the brush 109 from providing a uniformly
continuous contact pressure across the brush/surface interface, has
been observed to provide good chemical cleaning action when the
smooth brush 109 is rotated against surfaces of the substrate S1 in
the presence of cleaning chemicals, e.g., resulting in the reduced
adhesion of and/or dissolution of particles that tend to resist
removal via mechanical cleaning action.
[0026] FIG. 3 illustrates a process 300 for brush cleaning a
surface of a substrate S1. The process 300 may start at a step 301,
and proceed to a step 302.
[0027] In step 302, the substrate S1 is loaded into a first set of
brushes. For example, the substrate S1 may be loaded into the first
scrubbing apparatus 103 of FIG. 1 having the profiled brushes 105
of a nodular surface geometry as shown and described with respect
to FIG. 2A. Other types of apparatus may be employed, as may other
types of brushes (e.g., brushes having a substantially flat (rather
than cylindrical) brushing surface such as a `pancake` type brush).
Such pancake brushes may be of either the nodular or smooth
variety.
[0028] In a step 303, a first fluid is applied to the substrate S1.
The fluid may be, for example, an aqueous solution of NH.sub.4OH.
Deionized water or other chemistries alternatively may be applied.
One or more of many different methods and/or apparatus for applying
the first fluid to the substrate S1 may be employed, such as a
spray bar similar to the spray bar 117 of FIG. 1 via the first
fluid delivery apparatus 113, a pressurized delivery of the first
fluid outward of the brush surface via the pores of the brush
surface, etc., e.g., so long as the first fluid is permitted to
contact the surface of the substrate S1 so as to facilitate
cleaning thereof. The step 303 may accordingly occur before,
during, and/or after the step 302, e.g., as may be predetermined as
part of an overall cleaning recipe.
[0029] In a step 304, the surface of the substrate S1 is scrubbed
by the brushes described above with respect to the step 302. For
example, a profiled brush 105 such as is shown in FIG. 1 may be
closed against the major surface of the substrate S1 and rotated
relative to the substrate for a first time period (e.g., ten
seconds in duration) so as to create a mechanical cleaning action.
The fluid application function of step 303 may also occur during
the first time period in which the surface of the substrate S1 is
being scrubbed. The step of closing the scrubbing brush against the
substrate S1 may alternatively occur earlier, e.g., as part of one
of the steps 302 or 303.
[0030] In a step 305, the substrate S1 is loaded into a second set
of brushes. For example, the substrate S1 may be loaded into the
scrubbing apparatus 107 of FIG. 1 having the smooth brushes 109 of
a smooth surface geometry as shown and described with respect to
FIG. 2B. As in the step 302, other types of apparatus may be
employed, as may other numbers or types of brushes (e.g., pancake
brushes having a substantially planar brushing surface, rather than
a cylindrical-type brushing surface such as is shown in FIG. 1).
Further, although the step 305 may also include unloading the
substrate S1 from the first set of brushes of step 302 before
loading the substrate S1 into the second set of brushes of step
305, the step 305 may occur either before, simultaneously with, or
after the step 302. For example, a brush having two different
surface geometries or two or more brushes that have surface
geometries that are different from each other, may be employed in a
single scrubbing step.
[0031] In a step 306, a fluid is applied to the substrate S1. As in
step 303, the fluid used may be a chemistry, such as an aqueous
solution of NH.sub.4OH, it being also understood that other
chemistries or deionized water may be applied in addition or as an
alternative thereto. Also as in the step 303, one or more of many
different methods and/or apparatus for applying the fluid to the
substrate S1 may be employed, e.g., so long as the fluid is
permitted to contact the surface of the substrate S1 so as to
facilitate cleaning thereof. The step 306 may accordingly occur
before, during, and/or after the step 305.
[0032] In a step 307, the surface of the substrate S1 is scrubbed
by the brushes described above with respect to the step 305. For
example, a smooth brush 109 such as is shown in FIG. 1 may be
closed against the major surface of the substrate S1 and rotated
relative to the substrate for a second time period (e.g., twenty
seconds in duration) so as to create a cleaning action. The fluid
application function of step 306 may also occur as the surface of
the substrate S1 is scrubbed. As in the step 304, the step of
closing the brush against the substrate S1 may alternatively occur
earlier, e.g., as part of one of the steps 305 or 306. Also,
although especially good results may be achievable via the second
time period following the first time period without any overlap,
the first and second time periods of the steps 304 and 307 may
alternatively overlap and/or substantially coincide as is the case
when a substrate travels through a path defined by a plurality of
brushes (e.g., rather than rotating in place). The process 300 may
then end at a step 308.
[0033] Although the use in step 307 of the particular smooth brush
109 illustrated in FIG. 2B and described above may contribute to
overall improved chemical cleaning, other types of brushes than the
smooth brush 109 of FIG. 2B may be used, including one or more
embodiments of a brush that is relatively smooth with respect to
the brush used in the step 304, but which may not be entirely
smooth. For example, the brushes described above with respect to
step 305 may be of a surface geometry that is different from that
of the smooth brush 109 of FIG. 2B in that it contains surface
features that are of a scale of a tenth of a millimeter or larger,
but which are smaller by the same scale than the surface features
of the profiled brush 105 of FIG. 2A, such that a difference in
surface geometry in accordance with the present invention exists
between the brushes used in the step 304 and the brushes used in
the step 307.
[0034] The foregoing description discloses only particular
embodiments of the invention; modifications of the above disclosed
methods and apparatus which fall within the scope of the invention
will be readily apparent to those of ordinary skill in the art. For
instance, a horizontal orientation of the substrate S1 within a
scrubbing apparatus may be provided, rather than a vertical
orientation as shown in FIG. 1, and the scrubbing apparatus may be
equipped for scrubbing only one major surface and/or an edge
surface of the substrate S1, rather than two major surfaces as
shown. Also, if the steps 304 and 307 of the process 300 of FIG. 3
are performed sequentially, as opposed to simultaneously,
other/additional steps may intervene therebetween, such as one or
more rinsing steps (e.g., DI water rinse), and/or one or more
drying steps (e.g., Marangoni drying). The order of the steps 304
and 307 may be reversed, e.g., such that a smooth brush is used
first, followed by a profiled brush. Further, both brush types may
be incorporated within a single scrubbing apparatus, and/or the
substrate S1 may be caused to pass along and/or through a series of
brushes of different surface geometries, and as such may not need
to be rotated in place. As well, the present process need not
necessarily follow a chemical mechanical polishing (CMP) process.
Accordingly, other types of substrate processing other than CMP
processing may precede the present cleaning process, and/or the
present process may be performed in the absence of CMP
processing.
[0035] Accordingly, while the present invention has been disclosed
in connection with specific embodiments thereof, it should be
understood that other embodiments may fall within the spirit and
scope of the invention, as defined by the following claims.
* * * * *