U.S. patent application number 10/810421 was filed with the patent office on 2005-09-29 for rotatable valve.
Invention is credited to Jorg, Henderikus H.N.J..
Application Number | 20050211315 10/810421 |
Document ID | / |
Family ID | 34988366 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050211315 |
Kind Code |
A1 |
Jorg, Henderikus H.N.J. |
September 29, 2005 |
Rotatable valve
Abstract
A rotatable valve allows the flow of a fluid to be switched
between at least two different paths by rotating an element within
the valve. Advantageously, both the housing of the valve and the
rotatable element within the housing are formed of glass, making
the valve resistant to corrosion. The housing has at least three
openings for connecting to at least three different conduits. By
rotating the rotatable element, a flow path can be created between
a first of the conduits and either a second or a third one of the
conduits. Thus, the path between the first conduit and the second
conduit forms a first path, while the path between the first
conduit and the third conduit forms a second path.
Inventors: |
Jorg, Henderikus H.N.J.;
(Amerfoot, NL) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
34988366 |
Appl. No.: |
10/810421 |
Filed: |
March 25, 2004 |
Current U.S.
Class: |
137/625.47 |
Current CPC
Class: |
Y10T 137/86871 20150401;
Y10S 438/935 20130101; F16K 11/076 20130101; F16K 25/005 20130101;
F16K 27/0263 20130101 |
Class at
Publication: |
137/625.47 |
International
Class: |
F16K 011/076 |
Claims
We claim:
1. A valve, comprising: a glass valve housing having an inner
surface and at least three conduit connection openings; and a glass
rotatable valve element within the valve housing, the rotatable
valve element rotatable, about a valve element axis, between at
least two positions, wherein at least two of the at least three
conduit connection openings are disposed in the valve housing at
different angular positions relative to the rotatable valve element
axis, wherein the rotatable valve element comprises at least one
fluid passage having a first end and a second end, wherein the
first end aligns, in the at least two valve positions, to allow
deliberate fluid communication with a different one of the at least
two of the at least three conduit connection openings, wherein the
second end aligns to allow deliberate fluid communication with an
other of the at least three conduit connection openings, and
wherein a wall of the rotatable valve element is closely spaced
from the inner surface of the valve housing, between the at least
two conduit connection openings in the valve housing, such that
when the first end is aligned for deliberate fluid communication
with one of the at least two of the at least three conduits
connection openings, the first end is substantially separated from
an other of the at least two of the at least three conduit
connections openings by the wall of the rotatable valve element and
by the inner surface.
2. The valve of claim 1, wherein one of the at least three conduit
connection openings is a co-axial conduit connection opening that
is coaxial with the valve element axis.
3. The valve of claim 2, wherein the second end of the at least one
fluid passage is coaxial with the valve element axis, wherein the
co-axial conduit connection opening forms a contiguous path with
the at least one fluid passage.
4. The valve of claim 1, wherein the at least three conduit
connection openings comprises four conduit connection openings.
5. The valve of claim 4, wherein the rotatable valve element
comprises a second fluid passage, separated from the first fluid
passage, wherein the second fluid passage is configured such that
one pair of conduit connection openings is in deliberate fluid
communication via the first fluid passage when another pair of
conduit connection openings is in deliberate fluid communication
via the second fluid passage.
6. The valve of claim 5, wherein the second fluid passage is formed
by a recess in the wall of the rotatable element, wherein the
recess is open to the inner surface.
7. The valve of claim 6, wherein an other of the fluid passages has
one end coaxial with the valve element axis, wherein one of the
conduit connection openings is coaxial with the valve element axis
and wherein the other of the fluid passages forms a contiguous path
with the conduit connection opening that is coaxial with the valve
element axis.
8. The valve of claim 7, wherein one of the fluid passages is
connected in fluid communication with a process chamber.
9. The valve of claim 7, wherein another or the fluid passages is
connected in fluid communication with a fluid exhaust.
10. The valve of claim 1, wherein the inner surface of the valve
housing is cylindrical.
11. The valve of claim 1, further comprising one or more glass
conduits welded to the outside of the valve housing, wherein each
glass conduit is in fluid communication with one of the at least
three conduit connection openings.
12. The valve of claim 11, wherein the glass is quartz glass.
13. The valve of claim 1, wherein the rotatable valve element is
spaced from the valve housing by two seals, wherein each seal is
spaced from the fluid passages.
14. The valve of claim 13, wherein seals are glide bearings.
15. The valve of claim 14, wherein the seals comprise
polyvinylidene fluoride, polytetrafluoroethylene or the plastic
sold under the trademark TURCITE.RTM..
16. A valve for switching fluid flows, comprising: a cylindrical
rotatable part having a peripheral surface, the rotatable part
accommodated within an enclosure having an inner surface facing the
peripheral surface, wherein the enclosure comprises at least two
fluid input openings and a bypass opening, wherein the at least two
fluid input openings and the bypass opening are on one plane,
wherein the rotatable part comprises at least a peripheral fluid
passage and a second fluid passage, wherein the peripheral fluid
passage is formed by the inner surface and a groove extending
horizontally across the peripheral surface, wherein the groove is
coplanar with the at least two fluid input openings and the bypass
opening, wherein the second fluid passage has a second fluid
passage opening on the peripheral surface, wherein the second fluid
passage opening is coplanar with the at least two fluid input
openings and the bypass opening, wherein the rotatable part
comprises one or more dividers separating the peripheral fluid
passage from the second fluid passage, the one or more dividers
extending to the peripheral surface, and wherein the rotatable part
is configured to rotate to align the second fluid passage opening
with a first of the at least two fluid input openings in a first
position and with a second of the at least two fluid input openings
in a second position, wherein the groove is configured to fluidly
connect the second of the at least two fluid input openings with
the bypass opening when the rotatable part is in the first position
and wherein the groove is configured to fluidly connect the first
of the at least two fluid input openings with the bypass opening
when the rotatable part is in the second position.
17. The valve of claim 16, wherein the inner surface is separated
by about 0.1 mm or less from the peripheral surface.
18. The valve of claim 17, wherein the inner surface is separated
by about 0.04 mm or less from the peripheral surface.
19. The valve of claim 18, wherein the inner surface is separated
by about 0.02 mm or less from the peripheral surface.
20. The valve of claim 16, wherein the rotatable part and the
enclosure are formed of a corrosion resistant material.
21. The valve of claim 20, wherein the corrosion resistant material
is a glass.
22. The valve of claim 21, wherein the glass is chosen from the
groups consisting of lead glass, borosilicate glass and quartz
glass.
23. The valve of claim 20, wherein the rotatable part and the
enclosure are formed of the same corrosion resistant material.
24. The valve of claim 16, wherein, on the plane, an area of the
peripheral surface occupied by the groove is larger than an area of
the peripheral surface occupied by the second fluid passage
opening.
25. The valve of claim 16, wherein the groove is open to the inner
surface throughout a length of the groove.
26. A system for semiconductor processing, comprising: a
semiconductor process chamber; a fluid switching valve connected to
the chamber, wherein the valve comprises at least two fluid inputs
connected to a glass housing, wherein the valve further comprises a
rotatable glass element having a fluid passage, wherein the
rotatable element is configured to rotate to alternatingly form a
fluid flow path between the chamber, through the fluid passage, to
one or an other of the at least two fluid inputs.
27. The system of claim 26, wherein the chamber is part of a
floating substrate reactor.
28. The system of claim 27, wherein the reactor is the reactor sold
under the trademark LEVITOR.RTM..
29. The system of claim 26, further comprising a pneumatic cylinder
connected to the valve for rotating the rotatable element.
30. The system of claim 26, further comprising an exhaust connected
to the switching valve, wherein the chamber is dimensioned such
that fluid pressure in a flow path with the processing chamber is
larger than fluid pressure in a flow path with the exhaust.
31. The system of claim 26, programmed to deliver a sequence of
fluid flows from each of the at least two fluid inputs through the
chamber, wherein a magnitude of the fluid flows through the chamber
is substantially constant.
32. The system of claim 31, wherein the glass housing comprises an
exhaust, wherein the system is programmed to switch the at least
two fluid inputs between flowing into the chamber and flowing into
the exhaust.
33. The system of claim 32, programmed to process a plurality of
substrates one by one without stopping a flow of any fluid from the
at least two fluid inputs through the valve.
34. A method for semiconductor processing, comprising: loading a
substrate into a semiconductor process chamber; and switching a
flow of fluid into the reaction chamber by rotating a valve to
select between at least two fluid sources, wherein the valve
comprises a glass rotatable part accommodated within a glass
housing.
35. The method of claim 34, wherein the fluids are gases.
36. The method of claim 35, wherein the flow of the fluids
floatingly supports the substrate, wherein the substrate remains
floatingly supported throughout switching a flow of fluid.
37. The method of claim 34, wherein switching a flow of fluid
alternates the flow of fluid between a process gas flow and an
inert gas flow.
38. The method of claim 37, wherein the inert gas flow comprises
nitrogen gas.
39. The method of claim 37, wherein the process gas flow comprises
pyrogenic steam.
40. The method of claim 39, wherein the valve comprises an exhaust
and further comprising continuously generating pyrogenic steam and
flowing the steam out the exhaust when the inert gas is flowed into
the reaction chamber.
41. The method of claim 37, wherein a magnitude of each gas flow is
approximately equal.
42. The method of claim 41, wherein the magnitudes the gas flows
differ by about 20 percent or less.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to the field of fluid flow
control devices and, more particularly, to valves for switching
fluid flows.
[0003] 2. Description of the Related Art
[0004] In semiconductor process apparatuses involving a flow of
fluids, there is typically a need to control the magnitude of and
path taken by the fluids. For example, there is often a need to
switch fluid flows so that at one moment fluid flows from a source
along a first path and at another moment fluid flows from the
source along a second path.
[0005] An example of a process in which fluid flows are switched is
oxidation of silicon substrates by pyrogenic steam in a process
chamber. The pyrogenic steam is typically formed by combustion of
oxygen and hydrogen in a combustion chamber and the steam is then
fed from the combustion chamber into the process chamber. A
time-consuming procedure, known in the art, is typically followed
for the ignition of such a combustion chamber in order to ensure
safe operation and to prevent explosions. During the ignition
stage, the composition of the gas is not constant and,
consequently, is preferably flowed out an exhaust rather than into
the process chamber. After its composition has stabilized, the
steam can be directed into the process chamber.
[0006] In single wafer processing systems in which a series of
wafers is processed sequentially one by one, e.g., in wet oxidation
systems, it is very time consuming and uneconomical to ignite and
then switch-off the combustion chamber for processing each
individual wafer. It is more efficient to ignite the combustion
chamber at the start of the processing of the series of wafers and
to then switch it off when the processing of the entire series is
completed.
[0007] However, the loading and unloading of an individual wafer of
the series of wafers into and out of the processing chamber
preferably occurs in inert gas. This inert gas can be provided to
the chamber by establishing both a steam flow and an inert gas flow
and switching between the flows; for example, in one scenario the
steam flow is directed into the processing chamber and the inert
gas flow is directed to an exhaust, while in another scenario the
steam flow is directed to the exhaust and the inert gas flow is
directed into the processing chamber. Switching of the gas flows,
however, can easily result in flow and pressure fluctuations, which
are undesirable and can negatively affect process results.
[0008] In addition, the steam can be quite reactive with metal;
this concern is even greater in applications such as semiconductor
processing, where corrosive agents such as chlorine are often added
to the steam. Because the valves directing the gas flows are
typically metallic, these valves can become corroded and the
corrosion can lead to contamination of the ultra-pure steam. This
corrosion can also detrimentally affect the quality and purity of
the process results on the processed substrate.
[0009] Consequently, a need exists for a valve that swaps smoothly
and rapidly between at least two fluid flows and that is not as
susceptible to the issues noted above.
SUMMARY OF THE INVENTION
[0010] According to one aspect of the invention, a valve is
provided. The valve comprises a glass valve housing having an inner
surface and at least three conduit connection openings. A glass
rotatable valve element is provided within the valve housing. The
rotatable valve element is rotatable, about a rotatable valve
element axis, between at least two positions. At least two of the
at least three conduit connection openings in the valve housing are
disposed in the valve housing at different angular positions
relative to the rotatable valve element axis. The rotatable valve
element comprises at least one fluid passage having a first end and
a second end. The first end aligns, in the at least two valve
positions, to allow deliberate fluid communication with a different
one of the at least two of the at least three conduit connection
openings. The second end aligns to allow deliberate fluid
communication with an other of the at least three conduit
connection openings. A wall of the rotatable valve element is
closely spaced from the inner surface of the valve housing, between
the at least two conduit connection openings in the valve housing,
such that when the first end is aligned for deliberate fluid
communication with one of the at least two of the at least three
conduits connection openings, the first end is substantially
separated from an other of the at least two of the at least three
conduit connections openings by the wall of the rotatable valve
element and by the inner surface.
[0011] According to another aspect of the invention, a valve is
provided for switching fluid flows. The valve comprises a
cylindrical rotatable part having a peripheral surface. The
rotatable part is accommodated within an enclosure having an inner
surface facing the peripheral surface. The enclosure comprises at
least two fluid input openings and a bypass opening which are on
one plane. The rotatable part comprises at least a peripheral fluid
passage and a second fluid passage. The peripheral fluid passage is
formed by the inner surface and a groove extending horizontally
across the peripheral surface. The groove is coplanar with the at
least two fluid input openings and the bypass opening and is open
to the inner surface throughout a length of the groove. The second
fluid passage has a second fluid passage opening on the peripheral
surface. The second fluid passage is coplanar with the at least two
fluid input openings and the bypass opening. The rotatable part
also comprises one or more dividers separating the peripheral fluid
passage from the second fluid passage, with the one or more
dividers extending to the peripheral surface. The rotatable part is
configured to rotate to align the second fluid passage opening with
a first of the at least two fluid input openings in a first
position and with a second of the at least two fluid input openings
in a second position. The groove is configured to fluidly connect
the second of the at least two fluid input openings with the bypass
opening when the rotatable part is in the first position and is
also configured to fluidly connect the first of the at least two
fluid input openings with the bypass opening when the rotatable
part is in the second position.
[0012] In accordance with yet another aspect of the invention, a
system is provided for semiconductor processing. The system
comprises a semiconductor process chamber and a fluid switching
valve connected to the chamber. The valve comprises at least two
fluid inputs connected to a glass housing. The valve further
comprises a rotatable glass element having a fluid passage. The
rotatable element is configured to rotate to alternatingly form a
fluid flow path between the chamber, through the fluid passage, to
one or an other of the at least two fluid inputs.
[0013] According another aspect of the invention, a method is
provided for semiconductor processing. The method comprises loading
a substrate into a semiconductor process chamber and switching a
flow of fluid into the reaction chamber by rotating a valve to
select between at least two fluid sources. The valve comprises a
glass rotatable part accommodated within a glass housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The invention will be better understood from the Detailed
Description of the Preferred Embodiments and from the appended
drawings, which are meant to illustrate and not to limit the
invention, and wherein:
[0015] FIG. 1 is a cross-sectional side view of a rotatable glass
valve, in accordance with preferred embodiments of the
invention;
[0016] FIG. 2 is a top view showing the rotatable valve of FIG. 1,
in combination with a pneumatic cylinder, in accordance with
preferred embodiments of the invention;
[0017] FIG. 3 is a perspective view of the rotatable valve and
pneumatic cylinder of FIG. 2;
[0018] FIG. 4 is a cross-sectional view of the valve of FIG. 1,
taken along plane A-A of FIG. 1, the valve oriented in a first
position in accordance with preferred embodiments of the invention;
and
[0019] FIG. 5 is a cross-sectional view of the valve of FIG. 1,
taken along plane A-A of FIG. 1, the valve oriented in a second
position in accordance with preferred embodiments of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] In accordance with some preferred embodiments of the
invention, valves are provided that are resistant to corrosion. A
rotatable element, or part, within a valve housing, or enclosure,
can be rotated to form at least two different flow paths.
Preferably, both the rotatable element and the valve housing are
formed of a corrosion resistant material, which is preferably
glass. In addition, the openings forming the flow paths in the
rotatable element are preferably configured, as described below, so
that the physical distance between those openings is minimized.
Advantageously, this minimizes the time required to switch from one
path to another, thus minimizing pressure and flow fluctuations
downstream of the valve.
[0021] In addition, the valve is preferably connected to two or
more fluid sources, an exhaust and a destination for the fluid
flow, which is preferably a semiconductor process chamber. The
rotatable element preferably comprises a laterally extending cavity
or groove that allows at least some, and preferably all, source
connections, to be in fluid communication with the exhaust, which
is preferably at a lower pressure than the process chamber, when
not in deliberate fluid communication with the process chamber. In
this arrangement, fluids to be flowed into the process chamber can
be continuously generated and fluids not intended for flow into the
process chamber can be exhausted, thereby maintaining the purity of
the fluid flowing into the process chamber. Moreover, the seal
between the rotatable part and the housing need not be perfect,
because leaked fluids will tend to flow to the exhaust rather than
the process chamber due to the pressure differential between the
exhaust and the process chamber. Preferably, the pressure
difference between the exhaust and the process chamber is not so
large as to cause undesirable pressure fluctuations in the fluid
lines connected to the valve and/or in the process chamber,
especially when fluid flow paths are switched. Thus, the pressure
in the exhaust line is preferably only slightly lower than the
pressure in the reactor line.
[0022] The invention will now be described in further detail below
with reference to the appended drawings, wherein similar parts are
indicated with identical reference numerals throughout the
drawings.
[0023] In FIG. 1, a valve 10 according to preferred embodiments of
the invention is shown. A valve enclosure or housing 100, having an
inner surface 102 is provided with multiple conduit connection
openings, of which three, namely openings 140, 142, 144, are shown
in FIG. 1. The housing 100 is preferably formed of a corrosion
resistant material, more preferably a glass material. It will be
appreciated that a corrosion resistant material is a material that
is more resistant than metal to the corrosion caused by the steam
and halide mixtures used in semiconductor oxidation processes. The
valve housing 100 is also provided with a cover 120 which is
preferably formed of stainless steel, but which can be of any other
suitable construction material, including glass or Teflon.RTM.
(polytetrafluoroethylene). The cover 120 is preferably kept in
position against the valve housing 100 with bolts 130. The cover
120 is also preferably provided with a groove 122 to accommodate an
O-ring 124 to seal cover 120 against the upper end of the housing
100. At its bottom, the valve housing 100 is preferably mounted on
a base 110, which can be formed of any suitable construction
material known in the art, including glass or Teflon.RTM., but is
preferably also formed of stainless steel.
[0024] A rotatable valve element 200 is positioned within the valve
housing 100 and can be rotated relative to the valve housing 100.
The rotatable element 200 is preferably formed of a corrosion
resistant material, more preferably a glass material. It will be
appreciated that while the rotatable element 200 and the valve
housing 100 are preferably both formed of the same corrosion
resistant material, preferably both formed of glass, they can be
formed of different materials or different types of glass. In
addition, the valve housing 100 and the rotatable valve element 200
are both preferably cylindrical and dimensioned such that the valve
element 200 fits into the valve housing 100 with a sliding fit or a
close running fit, so that rotation of the rotatable valve element
200 is possible. Preferably, the outer diameter of the peripheral
surface or wall of the valve element 200 is less than about 0.1 mm,
more preferably less than about 0.04 mm and most preferably less
than about 0.02 mm smaller than the inner diameter of the inner
surface 102 of the valve housing 100. In this way, the valve
element 200 very tightly fits into the housing 100 and the small
gap between the valve element 200 and the valve housing 100 forms a
good barrier or seal for preventing fluid flow between them. The
valve element 200 is provided with or forms part of at least two
fluid passages, including, e.g., a peripheral fluid passage 212,
defined by a cavity in the valve element 200 and the inner surface
102, and a second fluid passage 210. The upper side of the valve
element 200 is preferably provided with a stem 222. The o-ring 124,
accommodated in a groove 122 in the cover 120, preferably provides
a seal between the valve element 200 and the cover 120.
[0025] The valve element 200 is preferably kept centered within the
housing 100 by bearings 220, which are preferably provided at the
upper and lower ends of valve housing 100. Suitable materials for
the bearings 220 include PVDF (polyvinylidene fluoride), more
preferably Teflon.RTM. (polytetrafluoroethylene) obtainable from
E.I. DU PONT DE NEMOURS of WILMINGTON DELAWARE, U.S.A., and, most
preferably, the bearings 220 are formed of Turcite.RTM. obtainable
from W. S. SHAMBAN, CULVER CITY CALIFORNIA, U.S.A. Advantageously,
the seals prevent the valve element 200 from directly mechanically
contacting with the valve housing 100. It will be appreciated that
direct glass-to-glass contact between the valve element 200 and the
valve housing 100 can result in abrasion, wear, and the formation
of particles, which is undesirable and has previously discouraged
use of glass as a material for forming a valve. Advantageously, it
has been found that materials such as Turcite.RTM. have properties
that are particularly well suited for use in glide bearings, such
as the bearings 220, to minimize the problems of abrasion, wear,
and particle formation. In addition, the spacing between the
peripheral surface of the valve element 200 and the inner surface
102 of the housing 100, discussed above, further minimize these
problems while also advantageously allowing for an adequate seal to
be formed between those surfaces.
[0026] With reference to FIGS. 1, 2 and 3, rotation of the valve
element 200 is preferably affected using a pneumatic cylinder 230.
FIGS. 2 and 3 show a top view and a side perspective view,
respectively, of the valve assembly and further illustrate the
connection of the valve 10 with the pneumatic cylinder 230,
according to a preferred embodiment of the invention. A valve stem
222 is preferably provided with a handle 224, which is preferably
rotatably connected to a pneumatic cylinder rod 228 through a
spindle 226. The pneumatic cylinder 230 is preferably mounted via a
plate 232 onto a bracket 234 for stability.
[0027] The valve housing 100 includes conduits 150, 152, 154 and
156, that are mounted at positions corresponding with conduit
connection openings in the rotatable valve housing 100, e.g.,
corresponding with connection openings 140, 142, 144 and 146 (FIGS.
1, 4 and 5), respectively. Preferably, the conduits 150, 152, 154
and 156 are also formed of glass and are welded onto the valve
housing 100. It will be appreciated that the glass for the valve
housing 100, valve element 200 and conduits 150, 152, 154 and 156
can be any glass available, including, without limitation, lead
glass and borosilicate glass, e.g., pyrex. Preferably, the glass is
a pure quartz glass, as quartz glass has an excellent corrosion
resistance and, because it is pure quartz, it does not exhibit the
leaching out of impurities which may occur with less pure
materials. It will be appreciated that the valve 10 and various
parts of that valve can be formed by various methods known in the
art for working with the materials used to form those parts,
including without limitation, machining and injection molding.
[0028] With reference to FIG. 1, in the valve position shown in
that Figure, the conduit connection opening 140 is in deliberate
fluid communication with the conduit connection opening 144 through
the fluid passage 210. The fluid passage 210 is a bore or channel
through the valve element 200 and preferably has two openings. The
upper part of fluid passage 210 is preferably radially oriented
and, in the valve position shown, preferably connects at its first
opening, at an outer end, with the conduit connection opening 140
and the lower part of the fluid passage 210 is preferably co-axial
with the valve element axis 205 and connects at a second opening,
at its lower end, with the conduit 154 via the conduit connection
opening 144. In turn, the conduit 154 leads to a process chamber
300 of a reactor 1. It will be appreciated that the reactor 1 can
be any reactor known to one of skill in the art of semiconductor
processing. It has been found that the valve 10 can advantageously
be used in conjunction with a floating substrate reactor, i.e., a
reactor in which a substrate is support floating on a cushion of
gas, such as the Levitor.RTM. reactor, available from ASM
International N.V. of Bilthoven, The Netherlands. The Levitor.RTM.
reactor is further described in U.S. Pat. No. 6,183,565 B1, the
entire disclosure of which is incorporated herein by reference.
[0029] FIG. 4 shows a cross section of the valve 10 as shown in
FIG. 1, taken along the plane A-A. As illustrated in FIG. 4 the
conduit 156 and the conduit connection opening 146 are preferably
aligned; the conduit 156 is provided in the valve housing 100 at a
location corresponding to the location of the conduit connection
opening 146. Thus, in the valve position shown, which is the same
valve position shown in FIG. 1, the conduit connection opening 142
is in deliberate fluid communication with the conduit connection
opening 146 through the fluid passage 212, which is a recess in the
peripheral part of the valve element 200.
[0030] As can be observed, the valve element 200 is preferably
provided with or forms part of at least two fluid passages, e.g.,
the fluid passage 210 and the fluid passage 212. The fluid passages
210 and 212 are preferably separated from each other by a divider
or wall 201 of the rotatable valve element 200 that extends between
the fluid passages 210, 212 and extends out to the circumference of
the valve element 200. As discussed above, the inner surface 102 of
the housing 100 is positioned proximate to the circumferential edge
of the divider 201 of the valve element 200, in order to form a
seal between the passages 210 and 212.
[0031] Preferably, the openings 140 and 146 are located less than
about 180 degrees apart to the amount that the rotatable valve
element 200 is rotated to align the passage 210 with the openings
140 and 146. This in turn advantageously reduces the amount of time
necessary to switch between the openings 140 and 146. It will be
appreciated, however, that in other embodiments having other
openings in addition to the openings 140 and 146, the openings 140
and 146 may be located about 180 degrees apart to make space for
the additional openings. However, where rapid switching between two
or more openings is desired, those openings are still preferably
spaced less than about 180 degrees part.
[0032] It will be appreciated that the divider or wall 201 is
preferably a portion of the valve element 200 that separates the
passages 210 and 212 and that, e.g., remains, on a plane with the
passages 210 and 212, after machining the valve element 200 to form
those passages 210 and 212. The thickness of the divider 201 is
preferably only as thick as necessary to form an adequate seal and
to ensure the structural integrity of the valve element 200. For
example, in the illustrated embodiment, the passages 210 and 212
are formed so that the divider 201 preferably only takes up as much
of the cross-sectional area of the valve element 200, on a plane
with the radially-extending portion of the passage 210, as
necessary to define the walls of the passage 210, while maintaining
an adequate seal and ensuring the structural integrity of the valve
element 200. As illustrated, on the plane with the
radially-extending portion of the passage 210, the remainder of the
cross-sectional area of the valve element 200 preferably is a
cavity that allows fluid flow between two or more other openings,
e.g., 142 and 146, in the housing 100. Thus, the passage 212 acts
as a bypass opening for fluid not flowing into the process chamber
1. Accordingly, the circumferential edge of the divider 201 is
preferably thin or narrow. In addition, by being closely spaced
from the inner surface 102, the circumferential edge of the divider
201 forms a narrow bridge along the peripheral surface of the valve
element 200 that substantially separates the openings 140 and 146
when the passage 210 is in communication with one or the other of
these openings.
[0033] Advantageously, such an arrangement allows for more rapid
switching of fluid paths, by minimizing the time that neither
opening 140 nor 146 is in communication with the passage 210.
Preferably, the openings 140, 142 and 146, the passage 212 and an
opening of the passage 210 are coplanar. As noted above, on this
plane, the passage 210 preferably occupies a smaller area on the
peripheral surface of the valve element 200 than the passage 212,
which is preferably connected to an exhaust. It will be appreciated
that when the divider 201 is made very thin, at some point during
the rotation of the rotatable valve element 200, all connection
openings 140, 142 and 146 may be in communication with each other
via the passage 212. Advantageously, however, in a configuration
where one of these openings leads to an exhaust, the mixed fluid
flow will be exhausted and this mixing of fluids will not enter the
process chamber 300 to detrimentally effect process results.
[0034] FIG. 5 shows the valve 10 of FIG. 2, with the valve element
200 rotated 90 degrees with respect to its orientation in FIG. 4.
Thus, the radial part of the fluid passage 210 is now shown
connecting with the conduit connection opening 146. As a result, in
this second valve position, the conduit connection opening 144 is
now in fluid communication with the conduit connection opening 146
via the fluid passage 210. Further, the conduit connection opening
140 is now in deliberate fluid communication with the conduit
connection opening 142 through the fluid passage 212.
[0035] Referring again to FIG. 1, it will be appreciated that, as
shown in the illustrated exemplary embodiments, the conduits 150
and 156 are preferably provided at their ends with a ball, to be
mated with a cup to form a fluid tight connection with a fluid feed
conduit. In addition, the conduit 154 is preferably provided at its
lower end with a groove and an O-ring 155, to seal with a process
chamber conduit. In addition, as noted above, the conduit 152 is
preferably an exhaust or bypass conduit that exhausts fluid out of
the valve assembly and away from the process chamber 300 preferably
attached to the conduit 154.
[0036] Thus, with reference to FIGS. 1, 4, and 5, the rotatable
valve 10 preferably comprises a cylindrical rotatable valve element
200 accommodated in a housing 100 that has a cylindrical inner
surface 102. Preferably, both the cylindrical rotatable valve
element 200 and the housing 100 are formed of glass. The rotatable
valve element 200 preferably has a single coaxial passage 210
extending from its bottom surface and terminating below its top
surface. At the bottom surface, the opening of the passage 210
aligns with a coaxial opening 144 in the housing 100. Near the
termination below the top surface, the passage 210 extends outward
radially and opens at the peripheral surface of the rotatable valve
element 200. The opening at the peripheral surface is positioned to
align with openings 140 and 146 in the housing 100 when the
rotatable valve element 200 is rotated. Preferably, the housing 100
also has an opening 142 which is connected to an exhaust. The
peripheral surface of the rotatable valve element 200 preferably
also has a tangentially extending recess that forms the passage
212. When the passage 210 is rotated to align with one or the other
of the openings 140, 146, the passage 212 is preferably positioned
to connect the other of the openings 140, 146 to the exhaust
opening 142. It will appreciated that the openings 140, 142, 144
and 146 can be connected to various fluid sources and/or
destinations, such as a semiconductor process chamber 300.
[0037] In one preferred method of semiconductor processing using
the above described valve 10, a first fluid flow, e.g., an inert
gas flow such as a nitrogen gas flow, is established and fed to the
conduit 150 and a second fluid flow, e.g., pyrogenic steam from a
combustion chamber, is established and fed to the inlet conduit 156
(FIGS. 4 and 5). During a first period, wherein the valve 10 is in
a first valve position (FIG. 4), the nitrogen gas flow is conducted
from the inlet conduit 150 via the fluid passage 210 and the
conduit 154 to the process chamber 300, whereas the pyrogenic steam
flow is conducted from the inlet conduit 156 via the fluid passage
212 and the conduit 152 to an exhaust. During this first period a
semiconductor substrate is preferably loaded into the processing
chamber.
[0038] Then, during a second period, or processing period, the
valve is switched to a second valve position, as shown in FIG. 5,
wherein the flows are swapped so that the nitrogen flow is now
conducted from the conduit 150 via the fluid passage 212 to the
conduit 152 out to the exhaust and the pyrogenic steam flow is
conducted from the conduit 156 via the fluid passage 210 to the
conduit 154 and into the processing chamber.
[0039] Switching the valve from the first valve position to the
second valve position can occur through operation of any mechanical
actuator capable of being connected to and rotating the rotatable
valve element 200. An example of such an actuator is the pneumatic
cylinder 230 of FIGS. 2 and 3. Advantageously, using a fast acting
actuator such as the pneumatic cylinder 230, the rotation can take
place in a fraction of a second, thereby minimizing any disruption
in gas flows through the process chamber 300. In addition, the
nitrogen flow and the pyrogenic steam flow are preferably of
approximately equal magnitude so that the magnitude of the flow
through the processing chamber is substantially constant,
magnitudes staying within about .+-.20% of each other; rather,
preferably, to minimize disturbances to the fluid flow through the
reaction chamber, only the gas composition changes.
[0040] Preferably, the process chamber 300 and the exhaust system
are dimensioned such that the pressure in the flow path towards the
processing chamber is slightly larger than the pressure in the flow
path to the exhaust so that any gas leakage through the narrow gap
between the peripheral or outer surface of the valve element 200
and inner surface 102 of valve body 100 is directed towards the
exhaust and not toward the processing chamber. Then the valve 10 is
switched back from the second valve position to the first valve
position so that the gas flows are swapped again and the nitrogen
flow is conducted again through the processing chamber 300 and the
steam flow is conducted to the exhaust. The valve 10 is maintained
in this valve position during a third period in which the
semiconductor substrate is unloaded from the processing chamber.
The operation described above can be repeated to process a series
of wafers.
[0041] It will be appreciated that the embodiments of the invention
offers numerous advantages, especially for alternatingly switching
the flow of a process gas and a purge gas into a single wafer
reactor, such as the Levitor.RTM. reactor. In a single wafer
reactor, the processing time for one wafer is very short and the
speed at which fluid switching occurs can have a significant impact
on process throughput. Advantageously, rapid switching between the
process gas and the purge gas increases the throughput of the
reactor.
[0042] Such rapid switching can be particularly advantageous in
processes in which a roughly equal flow of fluid is desirable. An
example of such a process is a wet oxidation in the Levitor.RTM.
reactor. In reactors such as the Levitor.RTM. reactor, a wafer is
supported floatingly by gas cushions between an upper section and a
lower section. The valve of the present inventions allows a process
gas flow and a purge gas flow of substantially equal magnitude to
be established, with rapid switching from one type of gas to the
other type of gas according, e.g., to instructions from a computer
program. A valve according to the illustrated embodiments allows
switching to occur so fast that the gas cushions for supporting the
wafer are not significantly affected and the wafer can be
floatingly supported in a constant manner, even when the gas flows
are repeatedly swapped. This allows accurately and independently
selecting the time that a wafer is exposed to a process gas in
accordance to the requirements of the process and obviates the need
for reestablishing and stabilizing the gas cushions after every gas
flow switch.
[0043] In addition, use of the valve 10 can be particularly
advantageous in the case of wet oxidation in which a torch is used
to form pyrogenic steam by the combustion of H.sub.2 in O.sub.2.
Typically the start-up procedure for generating a torch takes a
significant amount of time. With a valve according to the
invention, the torch can stay on throughout the sequential
processing of a series of wafers in a single wafer reactor,
alternatingly switching a flow of the pyrogenic steam between the
process chamber 300 and the exhaust conduit 152, while a flow of
purge gas is switched in the opposite manner, e.g., to flow out the
exhaust conduit 152 when the pyrogenic steam flows into the chamber
300 and to flow into the chamber 300 when the pyrogenic steam flows
out the exhaust conduit 152. Moreover, when made of glass, and in
particular quartz glass, a valve according to the described
embodiments is advantageously not attacked by water vapor, even
when chlorine-containing components are added to the water vapor.
Thus, it will be appreciated that the invention can be used in
numerous applications other than semiconductor processing. It is
especially advantageous, however, in applications where rapid fluid
flow switching and corrosion resistance are desirable.
[0044] It will be appreciated by those skilled in the art that
various omissions, additions and modifications may be made to the
methods and structures described above without departing from the
scope of the invention. All such modifications and changes are
intended to fall within the scope of the invention, as defined by
the appended claims.
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