U.S. patent application number 12/299302 was filed with the patent office on 2009-07-23 for wafer de-chucking.
This patent application is currently assigned to NXP B.V.. Invention is credited to Srdjan Kordic.
Application Number | 20090186560 12/299302 |
Document ID | / |
Family ID | 38655900 |
Filed Date | 2009-07-23 |
United States Patent
Application |
20090186560 |
Kind Code |
A1 |
Kordic; Srdjan |
July 23, 2009 |
WAFER DE-CHUCKING
Abstract
A carrier head (100) for a CMP tool, wherein the membrane (108)
defining a chamber with a contact surface (102) of the carrier head
(100) has a number of integral tubes (110) termining in openings
coupled directly to the substrate (106), in addition to a main
fluid flow passage (104) coupled to the chamber defined by the
membrane (108). In use, during loading and polishing, a vacuum is
applied to the main fluid flow passage (104) and the tubes (110) to
hold the substrate (106) in flat engagement with the membrane (108)
and contact surface (102). In order to unload the substrate (106),
fluid pressure is applied to the substrate (106) via the tubes
(110), whilst maintaining the application of the vacuum via the
main fluid flow passage (104) so as to minimise bending and
breakage of the substrate (106).
Inventors: |
Kordic; Srdjan; (Biviers,
FR) |
Correspondence
Address: |
NXP, B.V.;NXP INTELLECTUAL PROPERTY DEPARTMENT
M/S41-SJ, 1109 MCKAY DRIVE
SAN JOSE
CA
95131
US
|
Assignee: |
NXP B.V.
Eindhoven
NL
|
Family ID: |
38655900 |
Appl. No.: |
12/299302 |
Filed: |
April 30, 2007 |
PCT Filed: |
April 30, 2007 |
PCT NO: |
PCT/IB2007/051599 |
371 Date: |
October 31, 2008 |
Current U.S.
Class: |
451/36 ; 451/388;
451/398; 451/559 |
Current CPC
Class: |
B24B 37/30 20130101 |
Class at
Publication: |
451/36 ; 451/388;
451/398; 451/559 |
International
Class: |
B24B 41/06 20060101
B24B041/06; B24B 1/00 20060101 B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2006 |
EP |
06300423.8 |
Claims
1. A carrier head for a chemical mechanical polishing apparatus,
the carrier head comprising a contact surface on which is provided
a membrane for receiving a substrate to be polished, said membrane
forming a chamber with said contact surface, the carrier head
further comprising a main fluid flow passage coupled at one end to
said chamber and at an opposite end to means for creating a vacuum
or applying fluid pressure between said membrane and said contact
surface, said membrane comprising at least one opening from which
extends a respective fluid flow channel for selectively applying a
vacuum or fluid pressure directly to said substrate, when in
use.
2. A carrier head according to claim 1, wherein the respective
fluid flow channel that extends from the at least one opening in
said membrane comprises an integral tube.
3. A carrier head according to claim 1, comprising a respective
guide passage for receiving the or each fluid flow channel.
4. A carrier head according to claim 3, wherein the or each fluid
flow channel is received within a respective guide passage in
slidable engagement.
5. A carrier head according to claim 3, comprising a plurality of
concentric guide passages for receiving a plurality of respective
fluid flow channels extending from respective openings in said
membrane.
6. A carrier head according to claim 1, wherein said main fluid
flow passage is generally central relative to said contact surface
and substrate and said one or more membrane openings and respective
fluid flow channels are off-centre relative to said contact surface
and substrate.
7. A flexible membrane for use with a carrier head according to
claim 1, for forming a chamber with said contact surface, the
membrane comprising one or more openings from the or each of which
extends a respective fluid flow channel.
8. A method of performing chemical mechanical polishing in respect
of a substrate comprising the steps of providing a carrier head
according to claim 1, loading a substrate onto the contact surface
said carrier head against said membrane, and applying a vacuum to
said membrane via main fluid flow passage performing chemical
mechanical polishing in respect of said substrate, and unloading
said substrate by applying fluid pressure thereto via said at least
one opening and respective fluid flow channel whilst maintaining
the application of a vacuum to said membrane via said main fluid
flow passage.
9. A method according to claim 8, wherein during loading of said
substrate, vacuum is additionally applied to said substrate via
said at least one opening and respective fluid flow channel.
10. A fluid pressure control system for performing the method of
claim 8, in a carrier head according to claim 1, the fluid pressure
control system comprising an outlet coupled to said main fluid flow
passage and said one or more fluid flow channels and being
configured to operate in a first, loading mode, wherein a vacuum is
applied to said main fluid flow passage and said one or more fluid
flow channels for loading said substrate onto said carrier head and
performing chemical mechanical polishing in respect thereof, and a
second, unloading mode, wherein a vacuum is applied to said main
fluid flow passage and fluid pressure is applied to said one or
more fluid flow channels for unloading said substrate from said
carrier head.
Description
[0001] This invention relates generally to to a carrier head and,
more particularly, to a carrier head and membrane for chemical
mechanical polishing apparatus.
[0002] Integrated circuits are typically formed on substrates,
particularly silicon wafers, by the sequential deposition of
conductive, semiconductive or insulative layers. After each layer
is deposited and etched, the outer or uppermost surface of the
substrate, i.e. the exposed surface of the substrate, becomes
increasingly nonplanar. This nonplanar surface presents problems in
the photolithographic steps of the integrated circuit fabrication
process. Therefore, there is a need to periodically planarize the
substrate surface.
[0003] Chemical mechanical polishing (CMP) is one accepted method
of planarization. This method of planarization typically requires
that the substrate be mounted on a carrier or polishing head.
During polishing, the carrier head brings the exposed surface of
the substrate into contact with a rotating polishing pad and
provides a controllable load on the substrate to push it against
the polishing pad. A typical carrier head includes a flexible
membrane with an inner surface that encloses a chamber and an outer
surface that provides a substrate mounting surface. By controlling
the pressure in the chamber, the load applied to the substrate can
be varied.
[0004] Referring to FIG. 1a of the drawings, a typical CMP
apparatus comprises one or more carrier heads 10 having a flexible
membrane 12 sealed around an inner surface of the carrier head 10,
so as to define a chamber. A gas or fluid inlet/outlet 14 is
defined in the carrier head 10 which is in fluid communication with
the membrane 12. A pressure control assembly (not shown) is
provided for drawing air from the chamber defined by the membrane
12 or blowing air into the chamber.
[0005] In use, a substrate 16 is loaded into the carrier head 10 by
bringing it into contact with the membrane 12, and then a vacuum is
created via the outlet 14 to hold the membrane 12 and the substrate
16 flat against the inner surface of the carrier head. During
actual polishing, the vacuum is maintained and the carrier head 10
lowers the substrate 16 into contact with a polishing pad 18, and a
slurry acts as the media for chemical mechanical polishing of the
substrate (or wafer) 16. Thus the carrier head 10 loads and holds
the substrate 16 against the polishing pad 18. It will be
appreciated by a person skilled in the art that FIG. 1a is a
schematic diagram for illustrative purposes and that the polishing
pad 18 usually has a larger diameter than the head 10. During
polishing, the pad 18 is also in contact with the head via a
peripheral retaining ring which keeps the wafer from slipping away
during polishing. In addition, during polishing, wafer is pressed
against the pad by applying pressure to the membrane through the
inlet 14.
[0006] Referring to FIG. 1b of the drawings, during unloading (or
de-chucking) of a wafer 16 from the carrier head 10 of a CMP tool,
air is blown, via the inlet 14, into the chamber defined by the
membrane 12 so as to inflate it. In theory, this process is
intended to cause the wafer 16 to become dislodged from the
membrane 12. However, in practice, depending on the adhesion
between the wafer 16 and the membrane 12, the wafer may bend and
there is an increased risk that it may break. This risk is
especially aapparent if there are scratches on the wafer 16.
[0007] US Patent Application Publication no. 2003 236056 A1
describes an arrangement whereby lateral sprays are used to assist
wafer unloading by spraying fluid or gas between the wafer and the
membrane. In addition, there are lateral pins or blades (inserted
between the wafer and the membrane) that further assist by pulling
the wafer down. The disadvantage is that sprays may cause the wafer
to be blown in an undesired lateral direction if they are not well
balanced on all sides, and blades have an inherent risk of breaking
the wafer if the wafer sticks to the membrane.
[0008] It is therefore preferred to provide a carrier head and
membrane arrangement in general and for a CMP tool in particular,
whereby efficient unloading of a wafer from the carrier head is
achieved with reduced risk of breakage relative to prior art
arrangements.
[0009] In accordance with the present invention, there is provided
a carrier head for a chemical mechanical polishing apparatus, the
carrier head comprising a contact surface on which is provided a
membrane for receiving a substrate to be polished, said membrane
forming a chamber with said contact surface, the carrier head
further comprising a main fluid flow passage coupled at one end to
said chamber and at an opposite end to means for creating a vacuum
between said membrane and said contact surface, said membrane
comprising at least one opening from which extends a respective
fluid flow channel for selectively applying a vacuum or fluid
pressure directly to said substrate, when in use.
[0010] In a preferred embodiment, the respective fluid flow channel
that extends from the at least one opening in said membrane
comprises an integral tube. In a preferred embodiment, the carrier
head comprises a respective guide passage for receiving the or each
fluid flow channel. Beneficially the or each fluid flow channel is
received within a respective guide passage in slidable engagement,
such that movement of the membrane is not restricted during
polishing. In a preferred embodiment, the carrier head comprises a
plurality of concentric guide passages for receiving a plurality of
respective fluid flow channels extending from respective openings
in said membrane. Said main fluid flow passage is preferably
generally central relative to said contact surface and substrate
and said one or more membrane openings and respective fluid flow
channels are preferably off-centre relative to said contact surface
and substrate.
[0011] The present invention extends to a flexible membrane for use
with a carrier head as defined above for forming a chamber with
said contact surface, the membrane comprising one or more openings
from the or each of which extends a respective fluid flow
channel.
[0012] Also in accordance with the present invention there is
provided a method of performing chemical mechanical polishing in
respect of a substrate, comprising the steps of providing a carrier
head as defined above, loading a substrate onto the contact surface
said carrier head, against said membraine via main fluid flow
passage, performing chemical mechanical polishing in respect of
said substrate, and unloading said substrate by applying fluid
pressure thereto via said at least one opening and respective fluid
flow channel whilst maintaining the application of a vacuum to said
membrane via said main fluid flow passage.
[0013] Preferably, during loading of said substrate, a vacuum is
additionally applied to said substrate via said at least one
opening and respective fluid flow channel.
[0014] The present invention extends to a fluid pressure control
system for performing the method defined above in a carrier head as
defined above, the fluid pressure control system comprising an
outlet coupled to said main fluid flow passage and said one or more
fluid flow channels, and being configured to operate in a first
loading mode, wherein a vacuum is applied to said main fluid flow
passage and said one or more fluid flow channels for loading said
substrate onto said carrier head and performing chemical mechanical
polishing in respect thereof, and a second, unloading mode, wherein
a vacuum is applied to said main fluid flow passage and fluid
pressure is applied to said one or more fluid flow channels for
unloading said substrate from said carrier head.
[0015] These and other aspects of the present invention will be
apparent from, and elucidated with reference to the embodiments
described herein.
[0016] Embodiments of the present invention will now be described
by way of examples only and with reference to the accompanying
drawings, in which:
[0017] FIG. 1a is a schematic cross-sectional side view
illustrating the principal components of a carrier head of a CMP
tool according to the prior art, when a wafer has been loaded;
[0018] FIG. 1b is a schematic cross-sectional side view of the
carrier head of FIG. 1a during unloading of the wafer;
[0019] FIG. 2 is a schematic side view illustrating the principal
components of a carrier head according to an exemplary embodiment
of the present invention; and
[0020] FIG. 3 is a schematic view of a membrane for use with the
carrier head of FIG. 2;
[0021] Referring to FIGS. 2 and 3 of the drawings, a carrier head
100 according to an exemplary embodiment of the present invention
comprises an inner contact head 102 having a generally central main
inlet/outlet 104 for generating the vacuum required to hold the
wafer 106 flat against the membrane 108 and the polishing pad (not
shown) during polishing, as in the prior art arrangement described
with reference to FIG. 1 of the drawings.
[0022] However, in this case, referring especially to FIG. 3 of the
drawings, the membrane 108 is formed with a series of integral
tubes 110, and the contact head 102 is provided with a
corresponding series of slots or passages 112 for receiving the
membrane tubes 110. The main inlet/outlet 104 and the membrane
tubes 110 are connected to a fluid pressure control arrangement
(not shown). Thus, in the assembled configuration illustrated
schematically in FIG. 2 of the drawings, fluid flow through the
main inlet/outlet 104 is coupled to the membrane 108, whereas fluid
flow through the membrane tubes 110 is coupled directly to the
wafer 106.
[0023] In use, as before, a substrate 106 is loaded into the
carrier head 100 by bringing it into contact with the membrane 108,
and then a vacuum is created via the outlet 104 and the membrane
tubes 110 to hold the membrane 108 and the substrate 106 flat
against the inner surface of the contact head 102. During actual
polishing, the vacuum is maintained and the carrier head 100 lowers
the substrate 106 into contact with a polishing pad (not shown).
Subsequently, gas or fluid pressure is applied through inlet/outlet
104, which applies a pressure between the wafer 106 and the
polishing pad, and a slurry acts as the media for chemical
mechanical polishing of the substrate (or wafer) 106. Thus the
carrier head 100 loads and holds the substrate 106 against the
polishing pad. When the polishing process has been completed, the
vacuum is re-applied through the inlet/outlet 104 so as to enable
the carrier head 100 to lift the substrate 106 away from the
polishing head.
[0024] In this case, however, when it is required to unload (or
de-chuck) the substrate 106 from the carrier head 100, fluid (e.g.
air) pressure is applied by the fluid pressure control arrangement
directly to the substrate surface, via the membrane tubes 110,
whilst the vacuum continues to be maintained via the main
inlet/outlet 104 on the membrane 108. In this manner, the air
pressure, applied directly to the wafer 106 overcomes the adhesive
forces between the wafer 106 and the membrane 108 and causes the
wafer 106 to be released, while the continued vacuum provided via
the main inlet/outlet 104 prevents signfiicant inflation of the
membrane 108, and therefore prevents signficant bending of the
wafer 106.
[0025] The membrane tubes 110 are not affixed to the corresponding
guide passages 112 in the contact head 102. As such, the membrane
tubes 110 are mounted for slidable movement within the guide
passages 112 and membrane movement is thus substantially
unrestricted during polishing.
[0026] It should be noted that the above-mentioned embodiments
illustrate rather than limit the invention, and that those skilled
in the art will be capable of designing many alternative
embodiments without departing from the scope of the invention as
defined by the appended claims. In the claims, any reference signs
placed in parentheses shall not be construed as limiting the
claims. The word "comprising" and "comprises", and the like, does
not exclude the presence of elements or steps other than those
listed in any claim or the specification as a whole. The singular
reference of an element does not exclude the plural reference of
such elements and vice-versa. The invention may be implemented by
means of hardware comprising several distinct elements, and by
means of a suitably programmed computer. In a device claim
enumerating several means, several of these means may be embodied
by one and the same item of hardware. The mere fact that certain
measures are recited in mutually different dependent claims does
not indicate that a combination of these measures cannot be used to
advantage.
[0027] Furthermore, the invention may also be embodied with less
components than provided in the embodiments described here, wherein
one component carries out multiple functions. Just as well may the
invention be embodied using more elements than depicted in FIG. 3,
wherein functions carried out by one component in the embodiment
provided are distributed over multiple components.
[0028] A person skilled in the art will readily appreciate that
various parameters disclosed in the description may be modified and
that various embodiments disclosed and/or claimed may be combined
without departing from the scope of the invention.
[0029] It is stipulated that the reference signs in the claims do
not limit the scope of the claims, but are merely inserted to
enhance the legibility of the claims.
* * * * *