U.S. patent application number 11/926668 was filed with the patent office on 2008-03-13 for semiconductor wafer front side protection.
This patent application is currently assigned to International Business Machines Corporation. Invention is credited to Allan D. Abrams, Donald W. Brouillette, Joseph D. Danaher, Timothy C. Krywanczyk, Rene A. Lamothe, Ivan J. Stone, Matthew R. Whalen.
Application Number | 20080064185 11/926668 |
Document ID | / |
Family ID | 39170233 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080064185 |
Kind Code |
A1 |
Abrams; Allan D. ; et
al. |
March 13, 2008 |
SEMICONDUCTOR WAFER FRONT SIDE PROTECTION
Abstract
There is provided a method for making a wafer comprising the
steps of providing a substrate having a first surface, an opposite
second surface, and at least one side edge defining a thickness of
the substrate, the at least one side edge having a first peripheral
region and a second peripheral region adjacent to the first
peripheral region. The method includes applying a fluid to the
first surface and the first peripheral region of the at least one
side edge and removing the opposite second surface and the second
peripheral region of the at least one side edge to form a third
surface. A semiconductor chip made from the method for making the
wafer is also provided.
Inventors: |
Abrams; Allan D.; (Essex
Junction, VT) ; Brouillette; Donald W.; (St. Albans,
VT) ; Danaher; Joseph D.; (Hinesburg, VT) ;
Krywanczyk; Timothy C.; (Essex Junction, VT) ;
Lamothe; Rene A.; (Saint Albans, VT) ; Stone; Ivan
J.; (Bakersfield, VT) ; Whalen; Matthew R.;
(Chelsea, VT) |
Correspondence
Address: |
Driggs, Hogg, Daugherty & Del Zoppo Co., L.P.A.
38500 CHARDON ROAD
DEPT. IEN
WILLOUGHBY HILLS
OH
44094
US
|
Assignee: |
International Business Machines
Corporation
Armonk
NY
|
Family ID: |
39170233 |
Appl. No.: |
11/926668 |
Filed: |
October 29, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11117122 |
Apr 28, 2005 |
7288465 |
|
|
11926668 |
Oct 29, 2007 |
|
|
|
10413698 |
Apr 15, 2003 |
7001827 |
|
|
11117122 |
Apr 28, 2005 |
|
|
|
Current U.S.
Class: |
438/459 ;
257/E21.211 |
Current CPC
Class: |
H01L 21/3081 20130101;
H01L 21/304 20130101; H01L 2221/6834 20130101 |
Class at
Publication: |
438/459 ;
257/E21.211 |
International
Class: |
H01L 21/30 20060101
H01L021/30 |
Claims
1. A method for making a wafer comprising the steps of: providing a
substrate having a first surface, an opposite second surface, and
at least one side edge defining a thickness of said substrate, said
at least one side edge having a first peripheral region and a
second peripheral region adjacent to said first peripheral region;
chucking said substrate in a chuck with said first surface in
contact with said chuck; applying a fluid to said first surface and
said first peripheral region of said at least one side edge by
spraying a liquid stream against said first surface and said first
peripheral region of said at least one side edge of said substrate
at a pressure of from about 1 psi to about 20 psi; and removing
said opposite second surface and said second peripheral region of
said at least one side edge by grinding to form a third
surface.
2. A method for making a wafer comprising the steps of: providing a
substrate having a first surface, an opposite second surface, and
at least one side edge defining a thickness of said substrate, said
at least one side edge having a first peripheral region and a
second peripheral region adjacent to said first peripheral region;
chucking said substrate in a chuck with said first surface in
contact with said chuck; applying a fluid to said first surface and
said first peripheral region of said at least one side edge by
spraying a liquid stream against said first surface and said first
peripheral region of said at least one side edge of said substrate
for about one minute to about ten minutes; and removing said
opposite second surface and said second peripheral region of said
at least one side edge by grinding to form a third surface.
3. A method for making a wafer comprising the steps of: providing a
substrate having a first surface, an opposite second surface, and
at least one side edge defining a thickness of said substrate, said
at least one side edge having a first peripheral region and a
second peripheral region adjacent to said first peripheral region;
chucking said substrate in a chuck with said first surface in
contact with said chuck; applying a fluid to said first surface and
said first peripheral region of said at least one side edge by
spraying a liquid stream against said first surface and said first
peripheral region of said at least one side edge of said substrate
at a temperature of from about 20.degree. C. to about 40.degree.
C.; and removing said opposite second surface and said second
peripheral region of said at least one side edge by grinding to
form a third surface.
4. A method for making a wafer comprising the steps of: providing a
substrate having a first surface, an opposite second surface, and
at least one side edge defining a thickness of said substrate, said
at least one side edge having a first peripheral region and a
second peripheral region adjacent to said first peripheral region;
chucking said substrate in a chuck with said first surface in
contact with said chuck; applying a fluid to said first surface and
said first peripheral region of said at least one side edge by
spraying a liquid stream against said first surface and said first
peripheral region of said at least one side edge of said substrate
at a pressure of from about 1 psi to about 20 psi, for about one
minute to about 10 minutes, and at a temperature of from about
20.degree. C. to about 40.degree. C.; and removing said opposite
second surface and said second peripheral region of said at least
one side edge by grinding to form a third surface.
5. A method for making a wafer comprising the steps of: providing a
substrate having a first surface, an opposite second surface, and
at least one side edge defining a thickness of said substrate, said
at least one side edge having a first peripheral region and a
second peripheral region adjacent to said first peripheral region;
chucking said substrate in a chuck with said first surface in
contact with said chuck; applying a fluid to said first surface and
said first peripheral region of said at least one side edge by
blowing a gas stream against said first surface and said first
peripheral region of said at least one side edge of said substrate
at a pressure from about 1 psi to about 60 psi, for about one
minute to about 10 minutes, at a temperature of from about
20.degree. C. to about 40.degree. C.; and removing said opposite
second surface and said second peripheral region of said at least
one side edge by grinding to form a third surface.
6. The method for making the wafer of claim 4 wherein said step of
removing said opposite second surface and said second peripheral
region of said at least one side edge of said substrate comprises
grinding said wafer while applying a fluid to said first surface
and said first peripheral region of said at least one side edge by
blowing a liquid stream against said first surface and said first
peripheral region of said at least one side edge, and where said
grinding is performed using a grinding wheel including diamonds
having a size of from about 4 microns to about 60 microns in
diameter.
7. The method for making the wafer of claim 4 further including
polishing of said wafer.
8. The method of claim 5 wherein the first surface of said wafer is
free of any tape.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
11/117,122, filed Apr. 28, 2005, which will issue Oct. 30, 2007 as
U.S. Pat. No. 7,288,465 B2, and which is a continuation-in-part of
application Ser. No. 10/413,698, filed Apr. 15, 2003, now U.S. Pat.
No. 7,001,827.
FIELD OF THE INVENTION
[0002] The present invention generally relates to fabrication of
semiconductor chips and more particularly to a fabrication process
of a semiconductor chip wherein a first surface of the
semiconductor wafer, from which the semiconductor chip originates,
is protected by a fluid while an opposite surface of the wafer
undergoes a grinding and removal step. The invention also relates
to the semiconductor chip made from the fabrication process.
BACKGROUND OF THE INVENTION
[0003] In the fabrication process of semiconductor devices, such as
a semiconductor integrated circuit on a semiconductor wafer, it is
commonly practiced to divide the semiconductor wafer into
individual chips by a dicing process.
[0004] Before applying such a dicing process, it is generally
necessary to grind a surface of the wafer opposite a first surface
where the semiconductor devices are formed, such that the wafer has
a predetermined thickness. For example, such a grinding process can
be used to reduce the thickness of a wafer to 500 microns (.mu.) or
less according to the specification of the semiconductor
device.
[0005] In order to prevent damaging of the semiconductor wafer
from, for example, cracking at the time of grinding, it is commonly
practiced to protect the first side, commonly referred to as the
front side, of the wafer by an adhesive medium such as an adhesive
tape. Generally, the adhesive tape used for such a purpose carries,
on a tape base, an adhesive layer of an acrylic resin with a
thickness of about 30-40.mu.. The tape base, in turn, is formed of
a polymer such as a polyolefin, polyvinyl, or polyethylene and
generally has a thickness of about 100-150.mu..
[0006] After the grinding process, removal of the adhesive tape is
necessary. In order the help facilitate removal of the tape and
adhesive, the adhesive layer used for such a purpose is generally
added with a surfactant. By doing so, any adhesives remaining on
the substrate surface after tape removal can be more easily removed
by cleaning the wafer in purified water or in an organic solvent.
It should be noted that the composition of adhesives used in such a
tape changes substantially lot by lot, and the adhesive of the tape
tends to establish a very intimate adhesion with the wafer surface.
Adhesive residues often remain, such as amorphous carbon, nitrides
or amorphous polyimides, and extensive cleaning may be required.
Such a strong adhesion suggests that there is a cross-link reaction
between the adhesive and the residual materials on the wafer.
Sometimes up to 60 minutes or more of cleaning time may be
required. As the front side surface of the wafer generally includes
a film such as a polyimide or SiN, any tape adhesive remaining on
the wafer surface after tape removal, raises serious performance
problems.
[0007] Attempts have been made to use an adhesive tape that carries
a LV-cure type adhesive on the tape base for the purpose of the
protection of the wafer during the grinding process. When using
such a UV-cure type tape, an ultraviolet radiation is applied to
the wafer covered by the tape before removing the tape from the
wafer for facilitating the removal of the tape. As the adhesive is
cured as a result of the ultraviolet radiation, the adhesion of the
tape to the wafer is reduced substantially and removal of the tape
is achieved more easily. Adhesive residues can still remain even
with use of a UV-cure type adhesive. Furthermore, the use of a
UV-cure tape in the grinding process may cause a problem in the
fabrication of a semiconductor memory device that includes a
so-called floating gate, such as a flash memory or EEPROM. More
specifically, the initial data written into the floating gate of
the device may be erased or modified as a result of the ultraviolet
radiation. As a result, use of the UV-cure protective tape has not
been made a matter of common practice for fabricating semiconductor
devices.
[0008] It is possible to eliminate the cleaning process by applying
an ozone ashing process for a limited time interval against the
front side surface of the wafer after removal of the tape, such
that any remaining organic materials are oxidized. However, such an
ozone ashing process requires a huge facility investment and the
cost of the semiconductor is therefore increased. It is also
possible to apply a additional post-treatment process by using an
organic solvent such as isopropyl alcohol for removing any
remaining adhesive residues. Such a post-treatment inevitably
lowers the production through-put of the semiconductor chips.
[0009] A technique for fabricating a semiconductor chip wafer which
would eliminate the use of a protective tape during the grinding
process would be a substantial advance in packaging technology.
OBJECTS AND SUMMARY OF THE INVENTION
[0010] Accordingly, it is the object of this invention to enhance
the art of packaging technology.
[0011] It is another object of this invention to provide a method
of making a semiconductor wafer wherein a tapeless grinding process
is utilized.
[0012] It is yet another object of this invention to provide a
semiconductor chip that will be manufactured with a tapeless
grinding process having relatively lower manufacturing costs than
many current products.
[0013] According to one aspect of the invention there is provided a
method for making a wafer comprising the steps of providing a
substrate having a first surface, an opposite second surface, and
at least one side edge defining a thickness of the substrate, the
at least one side edge having a first peripheral region and a
second peripheral region adjacent to the first peripheral region.
The method includes applying a fluid to the first surface and the
first peripheral region of the at least one side edge and removing
the opposite second surface and the second peripheral region of the
at least one side edge to form a third surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIGS. 1(A) and 1(B) are diagrams showing a method of making
a wafer according to one embodiment of the present invention;
and
[0015] FIG. 2 is a diagrammatic sectional view of a wafer chucked
and gas flowing according to an embodiment of this invention
BEST MODE FOR CARRYING OUT THE INVENTION
[0016] For a better understanding of the present invention,
together with other and further objects, advantages and
capabilities thereof, reference is made to the following disclosure
and appended claims in connection with the above-described
drawings.
[0017] An embodiment of the present invention will now be described
referring to FIGS. 1(A) and 1(B). Each step will be explained in
order.
[0018] First, in step 1(A), a wafer 8 including a substrate 10
having a first surface 12 is provided. The wafer 10 can be
comprised of silicon, silicon germanium or gallium arsenide.
Substrate 10 includes an opposite second surface 14. First surface
12 of substrate 10 can include conductive circuit lines thereon
(not shown) comprised of aluminum, copper, gold, lead, tungsten,
and alloys thereof. First surface 12 of substrate 10 can also
include oxides, nitrides, and polysilicon thereon. Substrate 10
includes at least one side edge 16 defining a thickness of the
substrate, the side edge having a first peripheral region 18 and a
second peripheral region 20 adjacent to the first peripheral region
and second surface 14. Next, a fluid 22 is applied to first surface
12 and first peripheral region 18. The fluid 22 can be applied to
first surface 12 and first peripheral region 18 by spraying a
liquid or blowing a gas stream against the first surface and first
peripheral region. When a liquid is used the spray pressure is from
about 1 pound per square inch (psi.) to about 20 psi. When a gas is
used, it is blown onto the first surface and first peripheral
region at a pressure of from about 1 psi. to about 60 psi. Spraying
and blowing can be performed for about 1 minute to about 10 minutes
at a temperature of from about 20 degrees Celsius (.degree. C.) to
about 40.degree. C. Some examples of gases that can be used in the
invention are nitrogen, helium, carbon dioxide, air, and
combinations thereof. Some examples of liquids that can be used in
this invention are water or oils, such as mineral oil. Applying a
fluid to first surface 12 and first peripheral region 18
establishes a barrier around the first surface and first peripheral
region. This barrier prevents damage to these surfaces and the
conductive circuit lines on first surface 12 during subsequent
processing steps, performed on opposite second surface 14, such as
grinding, which will be described in more detail below.
[0019] Referring to FIG. 1(B), the next step in the process
comprises the step of removing opposite second surface 14 and
second peripheral region 20 of one side edge 16 to form a third
surface 24 (shown in phantom in FIG. 1(B) as it would exist after
completion of the removal step). The removal step can be performed
by a process such as grinding using a grinding wheel 26 having
diamonds 28 in contact with opposite surface 14 throughout the
grinding step. During the grinding step, a liquid, for example,
water can be used to assist in lubrication. Surface 14 is
continuously removed until it yields third surface 24 by the
grinding action of diamonds 28. The size of the diamonds can be
from about 4.mu. to about 60.mu. in diameter. Diamonds 24 are shown
as cross-sections of spheres, however the diamonds can also be
irregularly shaped. When diamonds 24 are irregularly shaped, the
widest dimension of any one diamond can be from about 4.mu. to
about 60.mu.. Other processes that can be used to remove opposite
second surface 14 and second peripheral region 20 are wet etching,
for example, with potassium hydroxide and plasma removal. Third
surface 24, even though shown as planar and flat can have features
of non-planarity and roughness due to the non-uniformity of the
grinding process. During the grinding step, particles of substrate
10 are generated. First surface 12 of substrate 10 must be
protected from these particles as well as from the grinding slurry.
This protection is provided by fluid 22 being applied to first
peripheral region 18 and first surface 12 and creating a barrier
therearound. The action of fluid 22 also provides a continuous
flushing action removing generated particles and grinding slurry.
The amount of grinding performed on substrate 10 can be defined by
the desired thickness of the substrate needed for semiconductor
chip performance. First edge portion 18 can have a thickness of
from about 50.mu. to about 725.mu. after grinding. After grinding
first surface 12 of substrate 10 may be polished. Polishing is
performed with a slurry. The slurry is a colloidal suspension of
silicon dioxide or aluminum dioxide in distilled water. Silicon
dioxide particles used are typically about 500 angstroms in size. A
base solution such as potassium hydroxide or sodium hydroxide can
be used to adjust the pH of the slurry, if desired. The substrate
10 is then washed with water, spun dry, diced to yield a plurality
of semiconductor chips.
[0020] In summary, the method of forming a wafer and the
semiconductor chip produced therefrom provide a semiconductor chip
that is less costly to produce and has low defect levels (higher
manufacturing yields) because the surface of the wafer from which
the semiconductor chip is formed and a first peripheral region of
at least one side edge of the semiconductor chip are protected from
the grinding process and its chemicals by the unique tapeless
process of the present invention. The unique method is less costly
because it eliminates use of tape, a detaping process, breakage of
the wafer associated with the detaping process, and avoids other
more costly alternatives proposed to remove tape from the wafer
when tape is utilized in the grinding process.
[0021] FIG. 2 shows, diagrammatically, a chucking device 30 holding
a wafer 10 for grinding according to an embodiment of this
invention. The chucking device 30 is formed of a porous material
such as a ceramic material preferably a chuck such as those
manufactured by Disco, Okamoto, or TSK. Thus fluids in the form of
gasses or liquids can pass through the material. A vacuum chamber
32 is provided at one side of the device 30 connected to a vacuum
pump 34 which will pull a vacuum in the vacuum chamber 32. Since
the chucking device 30 is formed of a porous material, the vacuum
in the chamber 32 will act to hold the wafer 10 to the opposite
side of the chucking device 30. The fluid 22 is supplied through an
annular opening 33 in the chucking device 30 from a fluid chamber
36 supplied by a pump 38 to flood the front side 12 and the side
wall 16 of the wafer 10. Moreover, the substrate 10 may be beveled,
and he vacuum will draw fluid to the center of the chuck. Thus the
patterns shown in FIGS. 1A and 1B are established and
maintained.
[0022] While there have been shown and described what are the
present considered preferred embodiments of the invention, it will
be obvious to those skilled in the art that various changes and
modifications may be made therein without departing from the scope
of the invention as defined by the appended claims.
* * * * *