U.S. patent application number 09/754510 was filed with the patent office on 2002-07-04 for rotary union for semiconductor wafer applications.
This patent application is currently assigned to SPEEDFAM-IPEC CORPORATION. Invention is credited to Garcia, John, Yednak,, Andrew III.
Application Number | 20020086617 09/754510 |
Document ID | / |
Family ID | 27623419 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020086617 |
Kind Code |
A1 |
Garcia, John ; et
al. |
July 4, 2002 |
ROTARY UNION FOR SEMICONDUCTOR WAFER APPLICATIONS
Abstract
A rotary union is provided for chemical/mechanical polishing of
silicon wafers, especially silicon wafers containing chemically
sensitive integrated circuit structures. A rotary union is provided
with a union rotor and union stator, coupled at the free end of a
support spindle carrying a CMP polishing table. In the preferred
embodiment the rotary union is joined to a coolant union forming
the lower end of the support spindle. A passageway through the
union rotor extends past the bottom end of the coolant union
rotating part to avoid contact of fluid transmitted through the
passageway formed in the union rotor, with the rotating part of the
coolant union.
Inventors: |
Garcia, John; (Morgan Hill,
CA) ; Yednak,, Andrew III; (Phoenix, AZ) |
Correspondence
Address: |
FITCH EVEN TABIN AND FLANNERY
120 SOUTH LA SALLE STREET
SUITE 1600
CHICAGO
IL
60603-3406
US
|
Assignee: |
SPEEDFAM-IPEC CORPORATION
|
Family ID: |
27623419 |
Appl. No.: |
09/754510 |
Filed: |
January 4, 2001 |
Current U.S.
Class: |
451/41 ; 451/446;
451/449; 451/450 |
Current CPC
Class: |
B24B 41/047 20130101;
B24B 37/04 20130101; B24B 57/02 20130101 |
Class at
Publication: |
451/41 ; 451/446;
451/449; 451/450 |
International
Class: |
B24B 001/00; B24B
007/19; B24B 007/30 |
Claims
What is claimed is:
1. A rotary union for mounting to a rotating element having an
element bore wall defining an element bore of preselected size, the
rotary union maintaining semiconductor wafer treatment fluids in an
ultra pure condition, the rotary union comprising: a union stator
having a support face; a union rotor having a support face and an
opposed mounting face adjacent the rotating element; at least one
mount for movably mounting the union rotor toward and away from the
rotating element; the union rotor defining a union bore of smaller
size than said element bore; a spring bias between said union rotor
mounting face and said rotating element, biasing said union rotor
away from said rotating element; a face seal between said union
stator support face and said the union rotor support face, said
face seal in the form of a flat washer and comprised of expanded
TEFLON material; and said union rotor defining a passageway for the
semiconductor wafer treatment fluids, said passageway extending
from said union rotor support face to a portion of said union rotor
mounting face radially interiorly of said element bore wall.
2. The rotary union of claim 1 wherein the union rotor mounting
face is stepped to form a collar portion extending into said
element bore wall, and said passageway extending through said
collar portion so as to be isolated from said element bore
wall.
3. The rotary union of claim 2 wherein said collar portion includes
a recess for receiving a flexible tubing.
4. The rotary union of claim 1 wherein said face seal is made of
GORE-TEX type GR material.
5. The rotary union of claim 1 wherein said union rotor and said
union stator are made of Polyethylene Terephthalate material.
6. The rotary union of claim 1 wherein said spring bias comprises a
spring in the form of a wave washer.
7. The rotary union of claim 1 wherein said at least one mount
comprises a shoulder bolt, and wherein said union rotor is free to
slide along a shoulder portion of the shoulder bolt.
8. The rotary union of claim 1 wherein said union rotor defines pin
recesses for receiving alignment pins extending from said
element.
9. The rotary union of claim 1 wherein said rotating element is
metallic.
10. A rotary union for mounting to a metallic rotating element
having an element bore wall defining an element bore of preselected
size, the rotary union maintaining semiconductor wafer treatment
fluids in an ultra pure condition, the rotary union comprising: a
union stator having a support face; a union rotor having a support
face and an opposed stepped mounting face adjacent the rotating
element; the union stator and the union rotor of nonmetallic
composition which maintains semi conductor wafer fluids in an ultra
pure condition; a plurality of elongated fasteners movably mounting
the union rotor toward and away from the rotating element; the
union rotor defining a union bore of smaller size than said element
bore; a spring bias between said union rotor mounting face and said
rotating element, biasing said union rotor away from said rotating
element; a face seal between said union stator support face and
said the union rotor support face, said face seal in the form of a
flat washer and comprised of expanded TEFLON material; and said
union rotor defining a passageway for the semiconductor wafer
treatment fluids, said passageway extending from said union rotor
support face to a portion of said union rotor mounting face
radially interiorly of said element bore wall.
11. The rotary union of claim 10 wherein the union rotor mounting
face is stepped to form a collar portion extending into said
element bore wall, and said passageway extends through said collar
portion so as to be isolated from said element bore wall.
12. The rotary union of claim 11 wherein said collar portion
includes a recess for receiving a flexible tubing.
13. The rotary union of claim 10 wherein said union rotor is made
of Polyethylene Terephthalate material.
14. The rotary union of claim 10 wherein said union rotor and said
union stator are made of Polyethylene Terephthalate material.
15. The rotary union of claim 10 wherein said spring bias comprises
a spring in the form of a wave washer.
16. The rotary union of claim 10 wherein said mount comprises a
shoulder bolt having a shoulder portion, and said union rotor is
free to slide along a shoulder portion of the shoulder bolt.
17. The rotary union of claim 10 wherein said union rotor defines
pin recesses for receiving alignment pins extending from said
element.
18. The rotary union of claim 10 wherein said element is
metallic.
19. The rotary union of claim 10 wherein said face seal is
comprised of GORE-TEX type GR material.
20. The rotary union of claim 10 wherein said metallic rotating
element comprises a rotor of a coolant union coupled to a support
spindle supporting a polishing table.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention pertains to rotary unions for
semiconductor wafer applications, such as chemical/mechanical
polishing. In particular, the present invention pertains to such
rotary unions which conduct a supply of "ultra pure" water which
contacts the semiconductor wafer and must therefore be chemically
compatible with the semiconductor wafer.
[0003] 2. Description of the Related Art
[0004] Silicon wafers are typically employed for the mass
production of commercially important integrated circuits. A
plurality of integrated circuit devices are formed on a silicon
wafer substrate, layer by layer, and chemical/mechanical polishing
(CMP) must be performed on the wafer,. between layering steps.
Layering is typically carried out using photolithographic
techniques which require an accurately flat surface.
[0005] Planarization of silicon wafers provides the high degree of
flatness required for integrated circuit fabrication using
photolithographic techniques. The active surface of the wafer
substrate is placed in contact with a rotating polishing pad in the
presence of various chemical agents which can include deionized
water, etchants and polishing slurries. The polishing of
commercially significant silicon wafers can include a more
aggressive material removal process in which a slurry of polishing
particles includes a chemically reactive agent. While it is
desirable to polish a semiconductor wafer as quickly as possible in
order to obtain the desired flatness or planarization, it is
important that the over polishing be avoided. This requires a
constant or near constant monitoring of the polishing process.
[0006] One type of polish monitoring employed today uses optical
and other types of sensors embedded in a polish table. As
mentioned, slurries and other types of chemical mixtures are
employed in chemical/mechanical polishing and other types of wafer
treatments. Typically, the polish table is flooded with slurry
which also covers or otherwise interferes with the monitoring
instrumentation. Accordingly, it is customary to wash the active
face of the monitoring instrumentation which may comprise, for
example, the free ends of optical wave guides embedded in the
polish table. A flushing medium is employed to displace slurry or
other wafer treatment chemicals from the active surface of the
monitoring instrumentation.
[0007] In addition to flushing away material from the active face
of the monitoring instrumentation, the flushing media must be
compatible with the semiconductor wafer in all respects, especially
in the sense of being chemically compatible with the wafer
substrate and the integrated circuit structures built on the water
substrate. Water is frequently chosen as the flushing medium since
it is relatively inert in many respects. However, even "pure" water
must be treated to attain very high levels of chemical inertness
with regard to the semiconductor wafer and the term "ultra pure"
has been applied to describe these special requirements. In order
to maintain its ultra pure qualities, even brief incidental contact
with metallic components must be avoided.
[0008] As mentioned, chemical/mechanical polishing is carried out
using a polishing table and accordingly a rotating support shaft is
customarily employed. In addition, devices used to contact the
wafer with the polishing pad are also rotationally driven. These
types of wafer-holding devices, usually termed wafer carriers,
oftentimes are called upon to supply a fluid as part of the wafer
treatment process. Thus, fluid communication must be maintained
between the rotating wafer carrier and an external, non-rotating
source.
[0009] Rotary unions, such as those described in U.S. Pat. No.
5,443,416 provides continuous fluid communication between a fluid
source and a fluid chamber associated with the rotating wafer
carrier. Although similar in some respects, a rotating polish table
is much more massive than typical wafer carriers, and is subjected
to much greater forces. If a rotary union is to be provided with
fluid communication, a different type of arrangement from those
employed in wafer carriers is needed. And, if a rotary union of a
polish table is required to provide continuous fluid communication,
different arrangements, other than those employed with wafer
carriers, must be provided. Solutions to these and other problems
attendant with polish table used in chemical/mechanical polishing
are continually being sought.
SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a
rotating union for a polish table used in chemical/mechanical
polishing of semiconductor wafers.
[0011] Another object of the present invention is to provide a
rotary union of the above type which provides a continuous fluid
communication from a remote stationary fluid source to the
polishing table and semiconductor wafers.
[0012] A further object of the present invention is to provide
rotating union of the above-described type which maintains the
desired condition of ultra pure fluids, such as ultra pure water,
as it flows through the rotary union to eventually contact directly
or indirectly, a semiconductor wafer being treated on the polishing
table.
[0013] These and other objects according to principles of the
present invention are provided in a rotary union for mounting to a
rotating element which has an element bore wall defining an element
bore of preselected size. The rotary union maintains semiconductor
wafer treatment fluids in an ultra pure condition and comprises a
union stator having a support face, a union rotor having a support
face and an opposed mounting face adjacent the rotating element and
at least one mount for movably mounting the union rotor toward and
away from the rotating element. The union rotor defines a union
bore of smaller size than said element bore. a spring bias between
said union rotor mounting face and said rotating element, biasing
said union rotor away from said rotating element, and a face seal
between said union stator support face and said the union rotor
support face, said face seal in the form of a flat washer and
comprised of expanded TEFLON material. The union rotor also defines
a passageway for the semiconductor wafer treatment fluids, said
passageway extending from said union rotor support face to a
portion of said union rotor mounting face radially interiorly of
said element bore wall.
[0014] Other objects according to principles of the present
invention are attained in a rotary union for mounting to a metallic
rotating element which has an element bore wall defining an element
bore of preselected size. The rotary union maintains semiconductor
wafer treatment fluids in an ultra pure condition and comprises a
union stator having a support face, a union rotor having a support
face and an opposed stepped mounting face adjacent the rotating
element, the union stator and the union rotor of nonmetallic
composition which maintains semiconductor wafer fluids in an ultra
pure condition, and a plurality of elongated fasteners movably
mounting the union rotor toward and away from the rotating element.
The union rotor defines a union bore of smaller size than said
element bore, a spring bias between said union rotor mounting face
and said rotating element, biasing said union rotor away from said
rotating element, and a face seal between said union stator support
face and said the union rotor support face, said face seal in the
form of a flat washer and comprised of expanded TEFLON material.
The union rotor defines a passageway for the semiconductor wafer
treatment fluids, said passageway extending from said union rotor
support face to a portion of said union rotor mounting face
radially interiorly of said element bore wall.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an exploded perspective view of a rotary union
according to principles of the present invention;
[0016] FIG. 2 is a cross-sectional view taken along the line 2-2 of
FIG. 1;
[0017] FIG. 3 is a cross-sectional view of a rotating polish table
and the rotary union of FIG. 2;
[0018] FIG. 4 is a fragmentary view of the bottom portion of FIG.
3, taken on an enlarged scale;
[0019] FIG. 5 is a cross-sectional view similar to that of FIG. 3,
but showing additional features of a monitoring instrumentation
system; and
[0020] FIG. 6 is a cross-sectional view taken along the line 6-6 of
FIG. 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] Referring now to the drawings, and initially to FIGS. 1 and
2, a rotary union 10 according to principles of the present
invention is shown in combination with a coolant union 12 having a
rotor portion 14 and a stator portion 16. The coolant union 12 is
supported from above by a polish table supporting spindle assembly
20 which includes a rotating spindle portion 22 and a stationary
spindle portion 24 (see FIG. 3). As will be described below, it has
been found convenient to secure rotary union 10 to coolant union
12. The rotary union 10 could also be connected directly to spindle
assembly 20, if desired, and such is contemplated by the present
invention. When the rotary union 10 is fit to the spindle shaft,
support bearings could be provided between the rotor and stator
members 30, 32 of rotary union 10. If desired, rotary union 10
could also be fit to a fluid distribution manifold.
[0022] Turning now to FIGS. 1-3, rotary union 10 comprises a
rotating part or union rotor 30 and a stationary part or union
stator 32. As shown in FIG. 3, threaded fasteners 36 extend through
holes 38 (see FIG. 2) to secure union stator 32 to the stationary
part 16 of coolant union 12. Referring to FIGS. 1 and 2, threaded
fasteners 42 having threaded portions 42b and shoulder portions 52a
secure union rotor 30 to the rotating part 14 of coolant union 12.
Preferably, fasteners 42 comprise shoulder bolts with shoulders
dimensioned sufficiently long as to permit union rotor 30 to
reciprocate back and forth along shoulder portions 42a, as
schematically indicated in FIG. 2 by a spacing 46 between shoulder
portion 42a and enlarged head 42c of fastener 42. Fasteners 42
function as a mount for movably mounting union rotor 30 toward and
away from rotating part 14 of coolant union 12. A spring member 48
is located between rotating part 14 of coolant union 12 and union
rotor 30, so as to bias union rotor 30 in a direction away from
rotating part 14 urging a lower face 30a of union rotary 30 toward
an opposing inner face 32a of union stator 32.
[0023] Disposed between opposed faces 30a and 32a of union rotor 30
and union stator 32 is a face seal 50 having the form of a flat
washer or disk with a central aperture 52 generally co-extensive
with a central aperture 54 of union stator 32. As can be seen in
FIG. 2, these apertures are generally co-extensive with an aperture
56 defined by rotating part 14 of coolant union 12. Referring to
FIG. 1, guide pins 60 in rotating part 14 of coolant union 12 align
union rotor 30 to coolant union 12. Alignment between the rotating
part of coolant union 12 and union rotary 30 is also provided by a
step portion 64 formed at the upper end of union rotor 30
dimensioned so as to be received in a central bore 66 defined by
rotating part 14 of the coolant union.
[0024] As can be seen, for example, in FIGS. 2 and 4, step portion
64 includes a recess or socket portion 70 for receiving a quick
connect fitting 72 of a flexible water tube 74 (see FIG. 4). With
reference to FIG. 2, recess 70 forms part of a passageway 80 which
extends through union rotor 30, having an enlarged portion 80a at
one end and an annular channel 80b at the other end. As can be seen
in FIG. 2, passageway 80 is aligned with a passageway 82 in face
seal 50 and a passageway 84 in union stator 32. A groove 86 formed
in the interior surface of union stator 32 communicates with
passageway 84. With reference to FIG. 4, a quick connect fitting 88
provides connection between an external fluid supply 90 and a
connection to passageway 80. It is generally preferred that face
seal 50 be secured to union stator 32 using adhesives or other
conventional securement arrangements. Thus, the surface of union
rotary 30 defining annular channel 80b wipes across the upper face
of seal 50. If desired, the arrangement could be reversed, with
face seal 50 secured to union rotor 30 and an annular groove formed
in union stator 32, communicating with passageway 84. In either
event, it is generally preferred that wear on face seal 50 be
limited to one of its two major surfaces. As a less preferred
alternative, face seal 50 could be made to move freely about both
of its major surfaces.
[0025] With reference to FIGS. 3 and 5, a polish table assembly 102
is mounted atop rotating spindle portion 22 and is rotatably driven
therewith, by a drive belt connected to drive sprocket 104.
Included in polish table 102 is polish monitoring instrumentation
108 which comprises conventional polish monitoring instrumentation,
such as optical end point determination equipment. As indicated in
FIG. 5, a face 110 of polish monitoring instrumentation 108 is
aligned with face 112 of polish table assembly 102. Included on
face 112 is a conventional polish pad (not shown).
[0026] In use, polish table face 112 is covered with slurry or
other CMP polishing media. In order to maintain the face 110 of
instrumentation 108 in an operational condition, face 110 is
flushed with suitable flushing media, such as ultra pure water
which is fed to surface 110 by flexible tube 74, which is connected
to union rotor 30 as explained above with reference to FIG. 4. A
supply of flushing medium is transported from an external source
90, thorough channel 80 in union rotor 30 so as to be received in
flexible tube 74. Thus, during rotation of table assembly 194, face
110 of instrumentation 108 is maintained in an operational (that
is, optically unobstructed) condition, with a continuous or
intermittent flow of flushing agent. With reference to FIG. 6, the
underside of the polish table is indicated at 120. A manifold
arrangement 122 and tubing 124 distributes flushing media to
selected points about the polish table to provide flushing for
multiple instrumentation locations.
[0027] In order to maintain the fluid traveling through rotary
union 10 in an ultra pure (fully wafer-compatible) condition, as
described, the fluid passageway is maintained separate from
contaminating materials such as the rotation part 14 of coolant
union 12, which is preferably made of a metallic composition. It
has been found, for example, that even if the rotating part 14 is
made of traditionally "pure" materials such as various stainless
steel compositions, some silicon wafer chemistries will be
negatively impacted if contacted by ultra pure water which even
briefly touches metallic rotating part 14 on its path toward the
surface of polish table assembly 102. Accordingly, as can be seen
for example in FIGS. 2 and 4, care is taken to maintain passageway
80 entirely within union rotary 30 and to extend passageway 80
beyond (i.e., downstream of) the lower face of rotating part 14 of
coolant union 12. As mentioned above, recess 70 (see FIG. 2) is
provided to receive a quick connector for flexible tube 74, shown
installed in FIG. 4. As can be seen for example in FIG. 4, a wall
portion 130 of union rotor 30 separates the fluid passageway from
the lower surface 132 of rotating part 14.
[0028] Chemicals, such as a flushing media, coming into contact
with the wafer circuits pass through the union rotor 30 before
coming into contact with its surfaces. As seen above, the fluid
pathway extends through union rotor 30 which provides shielding
from potentially incompatible materials conventionally employed in
polish table spindle arrangements. Union rotor 30 can be readily
manufactured with a minimum number of conventional machining steps
which can be employed with a wide variety of materials. A
particular advantage of the present invention is that different
materials can be readily substituted for the union rotor 30 without
a substantial increase in manufacturing costs. Thus, the present
invention contemplates that different materials may be used for the
fluid passageway, as may be dictated by so-called "wafer
chemistries" (a term which refers, for example, not only to
chemical interactions with the silicon wafer substrates, but also
the integrated circuit structures deposited thereon). Recently,
metallic circuits have been formed using copper alloys and other
materials which require a strict chemical regimen in order to avoid
undesirable effects, such as corrosion.
[0029] If subsequent operational changes raise issues of chemical
compatibility, union rotor 30 can be quickly and easily fabricated
from a different candidate material, thus expediting further
testing and evaluation. In the preferred embodiment, union rotor 30
is of monolithic construction, made from PET (polyethylene
terephthalate) also known as ERTALYTE. This union rotor material
has been chosen for its compatibility with chemical/mechanical
polishing of wafer compositions of current commercial interest.
While it is generally preferred that union rotor 30 be made of
non-metallic materials, it will be appreciated that a wide variety
of materials chosen according to their chemical compatibility with
wafer substrate and associated integrated circuit structures.
[0030] As can be seen for example in FIGS. 2 and 4, it is also
important that face seal 50 be compatible with fluids contacting
the wafer substrate and its structures. Additionally, face seal 50
must provide the wear characteristics and low friction qualities
necessary for rotational sealing of the union rotor with respect to
the union stator. In the preferred embodiment, face seal 50 is made
of expanded PTFE material and most preferably is made of type GR
PTFE material commercially available from GORE-TEX Corporation. The
GORE-TEX type GR material has been found to be sufficiently inert
for current commercial "ultra pure" water applications. That is,
this material was found to be chemically compatible and
non-contaminating with respect to commercially significant silicon
wafers and integrated circuit structures in use today. Further, the
GORE-TEX type GR material was found to be sufficiently hydrophobic,
contributing also to the heightened level of cleanliness required
for ultra pure applications. The chosen material was also found to
be very lubricious when employed in the manner indicated.
[0031] Over extended use, face seal 50 is prone to wear, so as to
take on a reduced thickness. Springs 58 urge union rotor 30 to
apply pressure against the face seal 50, so as to maintain its
desired operating characteristics, despite wear. Referring to FIG.
4, spring 48 preferably comprises a conventional wave spring made
of medium steel material. If desired, the wave spring 48 could be
replaced by conventional compression springs disposed about the
fasteners 42. It has been found preferable to "back up" spring 48
with a washer 140. Although the rotary part of fluid union 12 and
the union rotor 30 could be dimensioned for an accurate fit with
regard to a selected spring 48, it has been found convenient to
enlarge the spacing provided for spring 48 and to fill the space
with one or more washers 140, thereby providing a convenient
arrangement for controlling the end play and related forces exerted
on face seal 50. The aforementioned GORE-TEX type GR material held
its desired shape and lubricious properties under extended wear
conditions associated with relatively massive turntable
operations.
[0032] The drawings and the foregoing descriptions are not intended
to represent the only forms of the invention in regard to the
details of its construction and manner of operation. Changes in
form and in the proportion of parts, as well as the substitution of
equivalents, are contemplated as circumstances may suggest or
render expedient; and although specific terms have been employed,
they are intended in a generic and descriptive sense only and not
for the purposes of limitation, the scope of the invention being
delineated by the following claims.
* * * * *