U.S. patent application number 12/015944 was filed with the patent office on 2009-07-23 for electrostatic surface cleaning.
Invention is credited to Ajay Kumar, Banqiu Wu.
Application Number | 20090183322 12/015944 |
Document ID | / |
Family ID | 40875253 |
Filed Date | 2009-07-23 |
United States Patent
Application |
20090183322 |
Kind Code |
A1 |
Wu; Banqiu ; et al. |
July 23, 2009 |
ELECTROSTATIC SURFACE CLEANING
Abstract
Embodiments of the present invention generally provide apparatus
and methods for cleaning a substrate, such as a mask. One
embodiment of the present invention provides an apparatus for
cleaning a substrate comprising a substrate support configured to
receive and support the substrate, a collecting tip connected with
an electrostatic power source, wherein the collecting tip is
configured to pickup particles on a surface of the substrate using
electrostatic force, and an indexing mechanism configured to
provide relative movement between the collecting tip and the
substrate support.
Inventors: |
Wu; Banqiu; (Sunnyvale,
CA) ; Kumar; Ajay; (Cupertino, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP - - APPM/TX
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Family ID: |
40875253 |
Appl. No.: |
12/015944 |
Filed: |
January 17, 2008 |
Current U.S.
Class: |
15/1.51 |
Current CPC
Class: |
H01L 21/02041
20130101 |
Class at
Publication: |
15/1.51 |
International
Class: |
A47L 13/40 20060101
A47L013/40 |
Claims
1. An apparatus for cleaning a substrate, comprising: a substrate
support configured to receive and support the substrate; a
collecting tip connected with an electrostatic power source,
wherein the collecting tip is configured to pick up particles on a
surface of the substrate using electrostatic force; and an indexing
mechanism configured to provide relative movement between the
collecting tip and the substrate support.
2. The apparatus of claim 1, wherein the collecting tip comprises a
tapered end pointing at the surface of the substrate.
3. The apparatus of claim 2, wherein the size of the tapered end is
determined according to the size of the particles to be picked
up.
4. The apparatus of claim 1, wherein the collecting tip is mounted
near a moving end of a rotating arm and the indexing mechanism
comprises an arm actuator configured to rotate the rotating arm
about a fixed end of the rotating arm and to move the collecting
tip above the substrate support.
5. The apparatus of claim 4, wherein the indexing mechanism further
comprises a support actuator configured to rotate the substrate
support about a central axis of the substrate support.
6. The apparatus of claim 1, wherein the indexing mechanism
comprises a stage connected to the substrate support, and the stage
is configured to move the substrate support along x and y
coordinates.
7. The apparatus of claim 1, wherein the electrostatic power source
is configured to apply an electrostatic force between about 50 Volt
to about 250 Volt to the collecting tip.
8. The apparatus of claim 7, wherein the electrostatic force
applied to the collecting tip is between about 50 Volt to about 100
Volt.
9. An apparatus for removing particles from a substrate,
comprising: a substrate support configured to receive and support
the substrate; a probe assembly configured to remove particles from
the substrate, wherein the probe assembly comprises: an arm having
a free end and a fixed end, wherein the free end is movably
disposed above the substrate support; a collecting tip mounted near
the free end of the arm; and an electrostatic power source coupled
to the collecting tip, wherein the electrostatic power source is
configured to provide an electrostatic force to the collecting
tip.
10. The apparatus of claim 9, wherein the collecting tip has a
tapered end, and a size of the tapered end is determined by the
size of the particles to be removed.
11. The apparatus of claim 9, wherein the substrate support is
rotatable about a central axis of the substrate support, and the
arm is rotatable about the fixed end.
12. The apparatus of claim 9, further comprises an indexing stage
coupled to the substrate support, wherein the two dimension stage
is configured to move the substrate relative to the probe
assembly.
13. The apparatus of claim 9, wherein the electrostatic force is
between about 50 volt to about 250 volt.
14. The apparatus of claim 9, wherein the electrostatic force is
between about 50 volt to about 100 volt.
15. The apparatus of claim 9, wherein the substrate is a mask used
in a lithography process during semiconductor processing.
16. A method configured for cleaning a substrate, comprising:
providing a collecting tip configured to pick up particles from the
substrate; applying an electrostatic force to the collecting tip;
and moving the collecting tip towards the particles on the
substrate to pick up the particles.
17. The method of claim 16, wherein providing a collecting tip
comprises choosing a diameter of the collecting tip according to
sizes of the particles to be picked up.
18. The method of claim 16, wherein moving the collecting tip
comprises: rotating the substrate about a central axis of the
substrate while moving the collecting tip across the substrate from
the central axis outwards.
19. The method of claim 16, wherein moving the collecting tip
comprises: scanning the substrate using the collecting tip.
20. The method of claim 16, further comprising, prior to moving the
collecting tip, inspecting the substrate to locate the
particles.
21. The method of claim 16, further comprising, prior to applying
the electrostatic force, performing a wet cleaning to the
substrate.
22. The method of claim 16, wherein applying an electrostatic force
comprises applying an electrostatic power between about 50 volt to
about 250 volt to the collecting tip.
23. The method of claim 22, wherein the electrostatic power is
between about 50 volt to about 100 volt.
Description
BACKGROUND
[0001] 1. Field
[0002] Embodiments of the present invention generally relate to
methods and apparatus for cleaning a surface. Particularly,
embodiments of the present invention provide methods and apparatus
for removing particles from a surface of a substrate or a mask
during semiconductor processing.
[0003] 2. Description of the Related Art
[0004] As the trend continues to reduce the size of semiconductor
devices, the minimum particle size to be removed from substrates
and masks also decreases. For example, in extreme ultraviolet
lithography (EUVL), feature sizes can be 65 nm, 45 nm, 32 nm, or 22
nm, and the particles size limits are usually as small as 0.8 times
the feature sizes.
[0005] Various methods may be used to remove particles from
substrates or masks. For example, in one method, a substrate or
mask is irradiated by a laser with sufficient energy to release the
particles, while an inert gas flows across the wafer surface to
carry away the released particles. In another method an energy
transfer medium, typically a fluid, is interposed between each
particle to be removed and the surface. The medium is irradiated
with laser energy and absorbs sufficient energy to cause explosive
evaporation, thereby dislodging the particles.
[0006] However, the current methods are either limited in
applications or complicated to apply.
[0007] Therefore, there is a need for methods and apparatus to
cleaning particles of small sizes from a surface of a substrate or
a mask.
SUMMARY
[0008] Embodiments of the present invention generally provide
apparatus and methods for cleaning a substrate or a mask.
Particularly, the embodiments of the present invention provide
apparatus and methods for removing particles from a substrate or a
mask using electrostatic force.
[0009] One embodiment of the present invention provides an
apparatus for cleaning a substrate or a mask comprising a substrate
support configured to receive and support the substrate or the
mask, a collecting tip connected with an electrostatic power
source, wherein the collecting tip is configured to pick up
particles on a surface of the substrate or the mask using
electrostatic force, and an indexing mechanism configured to
provide relative movement between the collecting tip and the
substrate support.
[0010] Another embodiment of the present invention provides an
apparatus for removing particles from a substrate comprising a
substrate support configured to receive and support the substrate,
a probe assembly configured to remove particles from the substrate,
wherein the probe assembly comprises an arm having a free end and a
fixed end, wherein the free end is movably disposed above the
substrate support, a collecting tip mounted near the free end of
the arm, and an electrostatic power source coupled to the
collecting tip, wherein the electrostatic power source is
configured to provide an electrostatic force to the collecting tip
so that the collecting tip can remove particles from the
substrate.
[0011] Yet another embodiment of the present invention provides a
method configured for cleaning a mask or a substrate comprising
providing a collecting tip configured to pick up particles from the
mask or the substrate, applying an electrostatic force to the
collecting tip, and moving the collecting tip towards the particles
on the mask or the substrate to pick up the particles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] So that the manner in which the above recited features of
embodiments of the present invention can be understood in detail, a
more particular description of the invention, briefly summarized
above, may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0013] FIG. 1 schematically illustrates a side view of a cleaning
station in accordance with one embodiment of the present
invention.
[0014] FIGS. 2A-2B schematically illustrate enlarged views of a
collecting tip during a cleaning process in accordance with one
embodiment of the present invention.
[0015] FIG. 3 schematically illustrates a perspective view of a
cleaning station in accordance with one embodiment of the present
invention.
[0016] FIG. 4 schematically illustrates a perspective view of a
cleaning station in accordance with another embodiment of the
present invention.
[0017] FIG. 5 is a flow chart showing a cleaning process in
accordance with one embodiment of the present invention.
[0018] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one embodiment may be beneficially utilized on other
embodiments without specific recitation.
DETAILED DESCRIPTION
[0019] Embodiments of the present invention provide apparatus and
methods for removing particles from a substrate or a mask using
electrostatic force. In one embodiment, a collecting tip is coupled
to an electrostatic power source and is configured to pick up
particles from a substrate or a mask using electrostatic force when
approaching the particles. In one embodiment, the collecting tip
has a tapered end which has a diameter similar to size of the
target particles. In one embodiment, the tapered end is slightly
larger than the particles. In one embodiment, the target particles
are those larger than 80 percent of critical size of the features
on the substrate or mask being cleaned. Embodiments of the present
invention further provide an indexing mechanism configured to
generate relative movement between the collecting tip and the
substrate or mask so that the entire surface of the substrate or
mask may be cleaned.
[0020] FIG. 1 schematically illustrates a side view of a cleaning
station 100 in accordance with one embodiment of the present
invention. The cleaning station 100 may be configured to clean a
substrate or a mask alone or combined with other cleaning
processes. For example, the cleaning station 100 may be used to
clean masks or substrates after wet cleaning during pattern
generation.
[0021] The cleaning station 100 generally comprises a collecting
assembly 103 disposed above a substrate support 101 configured to
support a substrate/mask 102 thereon. In one embodiment, the
collecting assembly 103 comprises a collecting tip 104 mounted on a
mounting arm 109. The collecting tip 104 has a tapered end 105 free
from the mounting arm 109 and facing the substrate/mask 102. The
collecting tip 104 is electrically conductive and is coupled to an
electrostatic source 107.
[0022] The electrostatic source 107 generally comprises an
electrostatic generator configured to generate high voltages using
either friction or electrostatic induction to accumulate electric
charges. During cleaning, the collecting tip 104 is charged with
electrostatic charges which generate electrostatic force to attract
loose particles.
[0023] FIGS. 2A-2B schematically illustrate enlarged views of the
collecting tip 104 during a cleaning process in accordance with one
embodiment of the present invention. As shown in FIG. 2A, an
electrostatic field 110 is generated around the tapered end 105 of
the collecting tip 104 when the electrostatic source 107 provides
electrostatic charges to the collecting tip 104. As shown in FIG.
2A, particles 106 under the influence of the electrostatic field
110 may be picked up by the collecting tip 104, thus clearing up
from the surface of the substrate/mask 102. During the cleaning
process, it is not necessary for the collecting tip 104 to contact
the substrate/mask 102, thus preventing further contamination.
[0024] The collecting tip 104 may be charged positively or
negatively. In one embodiment, the electrostatic charge applied to
the collecting tip 104 may be in a range between about 50 volts to
about 250 volts. In another embodiment, the electrostatic charge
applied to the collecting tip 104 may be between about 50 volts to
about 100 volts.
[0025] In semiconductor manufacturing, the size of the particles to
be removed is generally determined by the critical dimension of the
features. For example, for a mask to be used in photolithography,
particles smaller than 0.8 times of technology node may be
tolerable. Therefore, any particles larger than 0.8 times of the
critical dimension of the features need to be removed. In one
embodiment, the tapered end 105 of the collecting tip 104 has a
diameter 108 slightly larger than the size 106a of the particles
106 to be removed.
[0026] In one embodiment, the collecting tip 104 may be fabricated
from a conductive material such as stainless steel and
titanium.
[0027] Referring back to FIG. 1, the cleaning station 100 further
comprises an indexing mechanism that provides relative movement
between the collecting tip 104 and the substrate/mask 102 as shown
by arrow 111. The relative movement allows the collecting tip 104
to access the entire top surface of the substrate/mask 102 to be
cleaned. Embodiments of the indexing mechanisms are further
described in FIGS. 3 and 4.
[0028] In one embodiment, the collecting tip 104 does not contact
the substrate/mask 102 during the cleaning process. The distance
112 between the top surface of the substrate/mask 102 and the
tapered end 105 of the collecting tip 104 may be less thank about
10 mm.
[0029] In another embodiment, the collecting tip 104 and the
substrate/mask 102 may move relatively along the vertical direction
as shown by arrow 113 of FIG. 1. The relative movement along the
vertical direction allows the collecting tip 104 to approach the
substrate/mask 102 for desired cleaning. In one embodiment, the
collecting tip 104 may move close to the substrate/mask 102 to be
in contact with the particles 106 to be cleaned during
cleaning.
[0030] FIG. 3 schematically illustrates a perspective view of a
cleaning station 200 in accordance with one embodiment of the
present invention.
[0031] The cleaning station 200 generally comprises a frame 215, a
collecting assembly 203 movably disposed on the frame 215, and a
substrate support 201 configured to support a substrate/mask 202
thereon.
[0032] The collecting assembly 203 comprises a collecting tip 204
mounted on a mounting arm 209. The collecting tip 204 has a tapered
end 205 free from the mounting arm 209 and facing the substrate
support 201. The collecting tip 204 is electrically conductive and
is coupled to an electrostatic source 207. The electrostatic source
207 is configured to provide electrostatic voltage to the
collecting tip 204.
[0033] The mounting arm 209 has a free end 209a where the
collecting tip 204 is mounted and a fixed end 209b coupled to the
frame 215. The mounting arm 209 is rotatable about an axis 211 near
the fixed end 209b so that the free end 209a and the collecting tip
204 are movable above the substrate support 201 as shown by curve
212. In one embodiment, the mounting arm 209 may also be movable
along vertical direction as shown by arrow 216 to allow adjustment
of elevations of the collecting tip 204.
[0034] The substrate support 201 is rotatable about a central axis
213. During a cleaning process, the substrate support 201 rotates
about the central axis 213 while the mounting arm 209 moves along
the curve 212 so that the collecting tip 204 scans through an
entire surface of the substrate/mask 202.
[0035] The cleaning station 200 may further comprise a tip
conditioning station 214 configured to remove collected particles
from the collecting tip 204. In one embodiment, the tip
conditioning station 214 may be disposed on the frame 215. Prior or
after cleaning a substrate/mask, the mounting arm 209 may rotate
towards the tip conditioning station 214 to have any particles on
the collecting tip 204 removed.
[0036] FIG. 4 schematically illustrates a perspective view of a
cleaning station 300 in accordance with another embodiment of the
present invention.
[0037] The cleaning station 300 generally comprises an indexing
stage 301 configured to movably support a substrate/mask 302 on a
top surface 301c. The indexing stage 301 comprises two drives 301a,
301b each configured to move the substrate/mask 302 independently
along a direction.
[0038] The cleaning station 300 further comprises a collecting
assembly 303 disposed about the stage 301. The collecting assembly
303 comprises a collecting tip 304 mounted on a mounting arm 309.
The collecting tip 304 has a tapered end 305 free from the mounting
arm 309 and facing the stage 301. The collecting tip 304 is
electrically conductive and is coupled to an electrostatic source
307. The electrostatic source 307 is configured to provide
electrostatic voltage to the collecting tip 304.
[0039] During cleaning, the substrate/mask 302 may be moved by the
indexing stage 301 so that the collecting tip 304 can scan through
the entire surface of the substrate/mask 302. Track 312 illustrates
an exemplary scanning path for a cleaning process.
[0040] In one embodiment, the collecting tip 304 may be movable
along vertical direction relative to the indexing stage 301 to
allow adjustment of elevations of the collecting tip 304.
[0041] In one embodiment, the indexing stage 301 may move the
substrate/mask 302 so that the collecting tip 304 is aligned with a
particle 306 to be removed. In one embodiment, the collecting tip
304 may be lowered to contact the particle 306 during the
removal.
[0042] FIG. 5 is a flow chart showing a cleaning process 400 in
accordance with one embodiment of the present invention. The
cleaning process 400 may be used during manufacturing of a mask for
photolithography or manufacturing of semiconductor devices on a
substrate.
[0043] Block 410 illustrates a pattern generating process wherein
features are formed on a substrate or a mask by removing or
depositing materials on certain areas.
[0044] Block 420 illustrates a wet cleaning process wherein
residuals on the substrate or the mask from the pattern generating
process are removed by a cleaning solution, such as a bulk cleaning
solution. After wet cleaning, the substrate/mask should be fairly
clean with only isolated particles remains thereon.
[0045] Block 430 illustrates an optional electrostatic cleaning
process after the wet cleaning. The electrostatic cleaning may be
scan cleaning using electrostatic cleaning stations described in
accordance with embodiments of the present invention.
[0046] Block 440 illustrates an inspection process wherein the
substrate/mask is probed to detect or locate any undesired
particles.
[0047] Block 450 illustrates an electrostatic cleaning process
after the inspection of block 440. The electrostatic cleaning may
be a scan cleaning or a targeted cleaning using electrostatic
cleaning stations described in accordance with embodiments of the
present invention. A scan cleaning is when an electrostatically
charged collecting tip scans the entire surface of the
substrate/mask to remove any particles. A targeted cleaning is when
an electrostatically charged collecting tip moves towards detected
particles and picks the detected particles up. This electrostatic
cleaning process is a fine cleaning compared to the wet cleaning
process of block 420.
[0048] Block 460 illustrates another inspection process. Generally,
the substrate/mask is ready for subsequent processing if no
undesired particle is found in this inspection. However, if there
are still remaining particles, process in blocks 450, 460 may be
repeated.
[0049] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *