U.S. patent application number 12/249961 was filed with the patent office on 2009-02-05 for single wafer method and apparatus for drying semiconductor substrates using an inert gas air-knife.
This patent application is currently assigned to APPLIED MATERIALS, INC.. Invention is credited to Younes Achkire, Timothy J. Franklin, Dan A. Marohl, Nathan D. Stein, Julia Svirchevski.
Application Number | 20090032068 12/249961 |
Document ID | / |
Family ID | 31720487 |
Filed Date | 2009-02-05 |
United States Patent
Application |
20090032068 |
Kind Code |
A1 |
Stein; Nathan D. ; et
al. |
February 5, 2009 |
SINGLE WAFER METHOD AND APPARATUS FOR DRYING SEMICONDUCTOR
SUBSTRATES USING AN INERT GAS AIR-KNIFE
Abstract
In one aspect, a method is provided. The method comprises
forming a meniscus at an interface between a substrate and a fluid
surface by moving the substrate through the fluid; shortening the
meniscus by applying an air knife to the meniscus at the interface
between the substrate and the fluid surface; and Marangoni drying
the substrate by applying a drying vapor to the shortened meniscus.
Numerous other aspects are provided.
Inventors: |
Stein; Nathan D.; (Mountain
View, CA) ; Achkire; Younes; (Los Gatos, CA) ;
Franklin; Timothy J.; (Campbell, CA) ; Svirchevski;
Julia; (San Jose, CA) ; Marohl; Dan A.; (San
Jose, CA) |
Correspondence
Address: |
DUGAN & DUGAN, PC
245 Saw Mill River Road, Suite 309
Hawthorne
NY
10532
US
|
Assignee: |
APPLIED MATERIALS, INC.
Santa Clara
CA
|
Family ID: |
31720487 |
Appl. No.: |
12/249961 |
Filed: |
October 12, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10461889 |
Jun 13, 2003 |
|
|
|
12249961 |
|
|
|
|
60388277 |
Jun 13, 2002 |
|
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Current U.S.
Class: |
134/30 |
Current CPC
Class: |
H01L 21/67034
20130101 |
Class at
Publication: |
134/30 |
International
Class: |
B08B 5/00 20060101
B08B005/00; B08B 3/04 20060101 B08B003/04 |
Claims
1. A method comprising: forming a meniscus at an interface between
a substrate and a fluid surface by moving the substrate through the
fluid; shortening the meniscus by applying an air knife to the
meniscus at the interface between the substrate and the fluid
surface; and Marangoni drying the substrate by applying a drying
vapor to the shortened meniscus.
2. The method of claim 1 wherein moving the substrate through the
fluid further comprises: inclining the substrate from a vertical
orientation.
3. The method of claim 2 wherein moving the substrate through the
fluid further comprises: lifting the substrate from a tank of fluid
along an inclined path.
4. The method of claim 3 wherein the substrate is lifted by a
substrate raising mechanism.
5. The method of claim 1 wherein forming the meniscus at the
interface between the substrate and the fluid surface further
comprises: forming a first meniscus at an interface between a first
side of the substrate and the fluid surface.
6. The method of claim 5 wherein forming the meniscus at the
interface between the substrate and the fluid surface further
comprises: forming a second meniscus at an interface between a
second side of the substrate and the fluid surface.
7. The method of claim 6 further comprising: applying a first
air-knife to the first meniscus.
8. The method of claim 7 further comprising: applying a second
air-knife to the second meniscus.
9. The method of claim 8 further comprising: setting a first and
second gas delivery angle.
10. The method of claim 9 further comprising: applying the first
air-knife at the first gas delivery angle, wherein the first gas
delivery angle is at an angle inclined downwardly from a horizontal
plane.
11. The method of claim 10 wherein the first gas delivery angle is
between 13.degree.-30.degree..
12. The method of claim 10 further comprising: applying the second
air-knife at the second gas delivery angle, wherein the second gas
delivery angle is at an angle inclined downwardly from the
horizontal plane.
13. The method of claim 12 wherein the first and second gas
delivery angles are different.
14. The method of claim 12 wherein the first and second gas
delivery angles are equal.
15. The method of claim 10 wherein the air-knife is applied to
applied to both hydrophilic and hydrophobic films on the substrate
at the same first gas delivery angle.
16. The method of claim 1 wherein the air-knife is a nozzle.
17. The method of claim 1 further comprising: employing gas flow
rates between 10-30 liters/minute via the air-knife.
18. The method of claim 12 further comprising: adjusting the first
and second gas delivery angles.
19. The method of claim 1 wherein Marangoni drying the substrate
further comprises: applying the drying vapor to the shortened
meniscus via the air-knife.
20. The method of claim 1 further comprising: employing a Marangoni
drying nozzle to supply the Marangoni drying vapor to the shortened
meniscus.
Description
[0001] This application is a division of, and claims priority to,
United States Non-Provisional patent application Ser. No.
10/461,889, filed Jun. 13, 2003, and titled, "SINGLE WAFER METHOD
AND APPARATUS FOR DRYING SEMICONDUCTOR SUBSTRATES USING AN INERT
GAS AIR-KNIFE," (Attorney Docket No. 7348) which claims priority to
U.S. Provisional Patent Application Ser. No. 60/388,277, filed Jun.
13, 2002, and titled, "SINGLE WAFER METHOD AND APPARATUS FOR DRYING
SEMICONDUCTOR SUBSTRATES USING AN INERT GAS AIR-KNIFE." (Attorney
Docket No. 7348/L) Both of these patent applications are hereby
incorporated by reference herein in their entirety for all
purposes.
FIELD OF THE INVENTION
[0002] This invention is concerned with semiconductor manufacturing
and is more particularly concerned with techniques for drying a
substrate.
BACKGROUND OF THE INVENTION
[0003] It is known to process a semiconductor substrate to achieve
a dry and low-contamination condition after processing steps such
as chemical mechanical polishing (CMP) and scrubbing. It has also
been proposed to employ immersion drying to semiconductor
substrates using the so-called Marangoni effect. An example of a
Marangoni dryer is disclosed in co-pending, commonly-owned U.S.
provisional patent application Ser. No. 60/335,335, filed Nov. 2,
2001 (Attorney Docket No. 5877/L), entitled "Single Wafer Immersion
Dryer and Drying Methods", and which is hereby incorporated herein
by reference in its entirety.
[0004] In Marangoni drying, a substrate is raised in a vertical
orientation from a fluid bath, and an alcohol vapor is delivered to
a meniscus that is formed at the substrate/fluid interface. The
alcohol vapor reduces the surface tension at the meniscus, thereby
creating a "Marangoni" force resulting in a downward liquid flow
opposite to the substrate lift direction. As a result, the
substrate surface above the meniscus is dried.
[0005] Marangoni drying is promising in terms of substrate
throughput, absence of water marks, and low contamination levels
achieved. However, it would be desirable to achieve comparable
results without the inconveniences of delivering and exhausting
hazardous alcohol vapor.
SUMMARY OF THE INVENTION
[0006] According to an aspect of the invention, a method of drying
a substrate is provided. The inventive method includes raising the
substrate out of a fluid bath. During the raising step, an
air-knife is applied to a meniscus formed at an interface between
the substrate and the surface of the bath.
[0007] As referred to herein, an air-knife is not limited to using
atmospheric air, but rather may use any suitable gas, including,
for example, an inert gas such as nitrogen or argon.
[0008] In another aspect of the invention, a method of drying a
substrate includes (1) setting a gas delivery angle for an air
knife used during an immersion-drying process; (2) using the air
knife during immersion drying of a hydrophilic substrate; and (3)
using the air knife during immersion drying of a hydrophobic
substrate. The gas delivery angle is unchanged during immersion
drying of both the hydrophilic substrate and hydrophobic
substrate.
[0009] It has been found that application of an air-knife to a
fluid meniscus in conjunction with substrate immersion drying
produces low contamination outcomes (e.g., with no water marks
formed on hydrophobic substrates), matching the performance of
Marangoni drying, with respect to absence of water marks and
acceptable throughput, while avoiding the use of alcohol vapor.
[0010] In a further aspect, a meniscus of rinsing fluid may be
formed on a substrate via a plurality of spray nozzles, rather than
via immersion in a bath. For example, a rinsing fluid may be
sprayed across the horizontal diameter of a vertically oriented
substrate as it leaves a vertically oriented scrubber. An air knife
may be applied at the meniscus or upper boundary of the rinsing
fluid on the substrate, to thereby dry the substrate.
[0011] 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 DRAWING
[0012] FIG. 1 is a schematic side view illustrating the inventive
apparatus and method;
[0013] FIG. 2 is a flow chart that illustrates a method of
operating the apparatus of FIG. 1; and
[0014] FIG. 3 is a schematic front elevational view of a scrubber
that may employ an air knife.
DETAILED DESCRIPTION
[0015] FIG. 1 is a schematic side view of a vertical single wafer
immersion drying apparatus 11 configured in accordance with the
present invention. For example, the principles of the present
invention may be applied to an immersion drying apparatus of the
type disclosed in the above-referenced co-pending U.S. provisional
patent application Ser. No. 60/335,335, filed Nov. 2, 2001. The
inventive immersion drying apparatus 11 includes a tank
schematically represented at reference numeral 13. The tank 13
contains a fluid bath 15 constituted by a rinsing fluid 17 such as
deionized water, a solution of a corrosion inhibitor such as BTA
(benzotriazole) or the like.
[0016] A substrate 19 that is being dried in the inventive
apparatus 11 is shown being raised in a substantially vertical
orientation from the fluid bath 15. The substrate 19 may be, for
example, a silicon wafer. A substrate raising mechanism
schematically represented by an arrow 21 is provided to raise the
substrate 19 from the fluid bath 15.
[0017] The substrate 19 has a front side 23 on which one or more
material layers have been and/or will be formed. The substrate 19
also has a back side 25 that is opposed to the front side 23.
During raising of the substrate 19, a first meniscus 27 of the
fluid 17 is formed at an interface 29 between the front side 23 of
the substrate 19 and a surface 31 of the fluid 17. A second
meniscus 33 is also formed at an interface 35 between the back side
25 of the substrate 19 and the fluid surface 31.
[0018] In accordance with the invention, a first air-knife,
schematically indicated by an arrow 37a, is applied to the meniscus
27 at the front side 23 of the substrate 19. The first air-knife
37a prevents the fluid 17 at the meniscus 27 from advancing
upwardly with the front side 23 of the substrate 19 as the
substrate 19 is raised, thereby drying the substrate 19. The first
air-knife 37a is applied at an angle 39 which is inclined
downwardly from a horizontal plane 41. The angle 39 will be
referred to as a "gas delivery angle". The gas delivery angle may,
for example, be in the range of 13.degree.-30.degree., depending on
the type of film formed on the substrate 19. Other gas delivery
angles may be employed.
[0019] As shown, a second air-knife 37b may be applied to the
meniscus 33 at the back side 25 of the substrate 19, to aid in
drying the back side 25 of the substrate 19. The back side gas
delivery angle may, but need not, be different from the front side
gas delivery angle. A different gas delivery angle may be preferred
for the back side if the surfaces on the two sides have different
characteristics. However, it is also contemplated to embody the
immersion drying apparatus 11 with an air-knife only at the front
side or back side of the substrate.
[0020] One advantage of the inventive immersion drying apparatus 11
including an air-knife applied to the fluid meniscus is that the
same gas delivery angle 39 may be used in connection with drying
both substrates having a hydrophilic film (e.g., TEOS) thereon and
also with substrates having a hydrophobic film (e.g., a low k
dielectric) thereon. In the absence of the air-knife 37a, the
meniscus 27 in the case of the substrate 19 having the hydrophilic
film thereon would extend higher above the surface 31 of the fluid
17 than the meniscus formed with a substrate having a hydrophobic
film thereon. However, the action of the air-knife 37a shortens or
deforms the meniscus formed on the hydrophilic film so that drying
may occur at substantially the same point above the fluid surface
31 as in the case of a substrate having a hydrophobic film
thereon.
[0021] In one embodiment of the invention, the air-knife 37a (or
37b) may be implemented by means of a nozzle (e.g., a spray tube;
not separately shown) of the same type as the gas delivery spray
tubes disclosed in the above-referenced co-pending provisional
patent application Ser. No. 60/335,335, filed Nov. 2, 2001. In
addition, a suitable gas supply (not shown) is coupled to the
nozzle. In one embodiment of the invention, the gas employed is
nitrogen (N.sub.2) although other gases may be used.
[0022] In a particular embodiment, a nozzle tube having a
perforated length of about 8.5 inches (which may be used, for
example, in drying a 200 millimeter wafer) and having 114 holes of
0.005-0.007 inches in diameter, uniformly distributed along the
perforated length of the nozzle tube may be used. The holes
preferably should all be colinear and have the same orientation.
The nozzle tube may be formed of stainless steel, quartz, or
another suitable material. Other configurations may be
employed.
[0023] With such a nozzle tube, a gas flow rate of 15 liters per
minute may be employed. Higher or lower gas flow rates could also
be employed. For example, gas flow rates in the range of 10-30
liters/minute are specifically contemplated. In one embodiment, a
gas delivery angle of 15.degree. was found to be suitable for both
hydrophilic and hydrophobic wafer surfaces. It is believed that
this angle would also be appropriate for a patterned wafer surface
having both hydrophilic and hydrophobic features. Further, it has
been found that gas delivery angles in the range of
10.degree.-20.degree. may be preferred for drying a wafer having a
hydrophilic film (TEOS).
[0024] In the same embodiment, the substrate 19 was raised while
being inclined away from the front side air-knife nozzle tube at an
angle of 9.degree. from the vertical. The direction of motion of
the substrate was in the inclined plane defined by the substrate,
as in the immersion tank disclosed in the above-referenced
co-pending provisional patent application Ser. No. 60/335,335,
filed Nov. 2, 2001.
[0025] The cross-sectional center of the nozzle tube was a distance
of 0.36 inches above the fluid surface, and at a perpendicular
distance from the wafer surface of 0.63 inches for the front-side
nozzle. For the back-side nozzle, the perpendicular distance to the
wafer was 0.51 inches. In this same embodiment, the speed of
raising the substrate was 2.5 millimeters per second. However,
satisfactory results have also been obtained with a speed of
raising the substrate of 10 millimeters per second. There may be,
in general, a trade off between substrate-raising speed and number
of contaminants after the drying process, with higher
substrate-raising speeds possibly resulting in a greater number of
contaminants.
[0026] FIG. 2 is a flow chart that illustrates a method of
operating the apparatus of FIG. 1. Initially, in step 51, the gas
delivery angle is set (e.g., at 150). The setting of the gas
delivery angle may be performed, for example, by fixedly mounting
an air knife 37a and/or 37b (e.g., one or more nozzle tubes)
relative to the tank 13. Alternatively, each nozzle tube may be
adjustably mounted relative to the tank 13 and may be manually or
otherwise adjusted to set the gas delivery angle.
[0027] Next, at step 53, one or more hydrophobic substrates (i.e.,
substrates having a hydrophobic film on the front side thereof) are
immersion-dried using an air-knife in accordance with the
invention, with the gas delivery angle set at step 51.
[0028] Following step 53 is step 55, at which one or more
hydrophilic substrates (i.e., substrates having a hydrophilic film
on the front side thereof) are immersion-dried using an air-knife
in accordance with the invention, with the gas delivery angle set
at step 51.
[0029] It will be noted that the gas delivery angle is not changed
between steps 53 and 55.
[0030] The order of steps 53 and 55 may be reversed, and again it
is not necessary to change the gas delivery angle between the two
steps.
[0031] The air-knife may be implemented using structure that is
different from the nozzle tube described above. Gas flow rate may
be varied and/or a gas other than nitrogen (N.sub.2) may be
employed.
[0032] The present invention may be applied to drying a substrate
having a different size and/or a different shape than a 200 mm
wafer (e.g., a square or rectangular glass substrate such as
employed for flat panel displays). The length of the nozzle tube
may be varied as appropriate.
[0033] The substrate may be raised at an angle other than 9.degree.
from the vertical, or may be raised without inclination (i.e., at
90.degree. from the horizontal).
[0034] The air-knife/nozzle tube may be arranged so that the gas
delivery angle is adjustable by, e.g., manual adjustment.
[0035] An alcohol vapor (e.g., isopropyl alcohol vapor) or another
gas or vapor that serves to lower the surface tension of the
rinsing fluid (i.e., a Marangoni drying gas) may be included in the
gas dispensed by the air-knife nozzle tube (e.g., by the type of
arrangement disclosed in the above-referenced co-pending
provisional patent application Ser. No. 60/335,335, filed Nov. 2,
2001) so that Marangoni effect drying is also employed in the
inventive immersion drying apparatus. Alternatively, a separate
Marangoni drying nozzle 43a, 43b (shown in phantom in FIG. 1) may
be employed to supply Marangoni drying gas to a meniscus. The
Marangoni drying nozzle 43a, 43b may be employed in addition to the
air-knife 37a, 37b that manipulates the meniscus. By employing both
an air-knife and a Marangoni drying gas, consecutive drying of
hydrophilic and hydrophobic surfaces (or vice versa) may be
employed without needing to adjust the position of the Marangoni
drying nozzle 43a, 43b. Specifically, because the air-knife 37a,
37b manipulates the meniscus 27, 33 to the same position for both
hydrophilic and hydrophobic surfaces, the Marangoni drying nozzle
43a, 43b may maintain the same position for drying of hydrophilic
surfaces and hydrophobic surfaces. Accordingly, throughput may be
increased and labor costs decreased.
[0036] Moreover, with use of the present invention (with or without
application of a Marangoni drying gas) surfaces having both
hydrophilic and hydrophobic portions (such as patterned
semiconductor wafers) may be dried with better results (e.g., fewer
contaminants).
[0037] In a further aspect, the invention may be employed within a
vertically oriented scrubber. FIG. 3 is a schematic front
elevational view of a vertically oriented scrubber 101, having a
plurality of rollers 303 for supporting a substrate S. A front side
and a back side scrubber brush 305 (only one shown) are positioned
above the rollers 303 so as to contact the front and back sides of
the substrate S positioned on the rollers 303. A fluid spray nozzle
307 is positioned above the scrubber brushes 305, and an air knife
nozzle 309 is positioned above the fluid spray nozzle 307. An
optional Marangoni drying nozzle 311 (shown in phantom) may be
included. After the substrate S is scrubbed it may be dried via the
air knife nozzle 309 (with or without the aid of a Marangoni drying
vapor supplied either via the air knife nozzle 309 or via the
Marangoni drying nozzle 311) in the manner described above with
reference to FIGS. 1 and 2, as the substrate S is lifted from the
rollers 303 (e.g., via a wafer handler or substrate pusher, not
shown). Note that the rinsing fluid nozzle 307, the Marangoni
drying nozzle 311 and the air knife nozzle 309 preferably are
positioned above the upper perimeter of the substrate S when the
substrate S is positioned on the rollers 303. In this manner the
entire substrate surface is lifted past the nozzles 307-311. A
second set of nozzles 307-311 may be similarly positioned along the
back side of the substrate S.
[0038] The foregoing description discloses only exemplary
embodiments of the invention. Modifications of the above disclosed
apparatus and method which fall within the scope of the invention
will be readily apparent to those of ordinary skill in the art. For
instance, a substrate may be held at any orientation while being
dried by an air knife. As stated, the present invention may be
employed, for example, within a system similar to that described in
previously incorporated U.S. Provisional Patent Application Ser.
No. 60/335,335, filed Nov. 2, 2001 (Attorney Docket No. 5877/L),
entitled "Single Wafer Immersion Dryer and Drying Methods" or
within any other suitable system.
[0039] Accordingly, while the present invention has been disclosed
in connection with exemplary 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.
* * * * *