U.S. patent application number 11/142087 was filed with the patent office on 2005-10-06 for gas distribution system.
This patent application is currently assigned to Aviza Technology, Inc.. Invention is credited to DeDontney, Jay Brian, Yao, Jack Chihchieh.
Application Number | 20050217580 11/142087 |
Document ID | / |
Family ID | 33511648 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050217580 |
Kind Code |
A1 |
DeDontney, Jay Brian ; et
al. |
October 6, 2005 |
Gas distribution system
Abstract
The present invention provides a gas distribution apparatus
useful in semiconductor manufacturing. The gas distribution
apparatus comprises a unitary member and a gas distribution network
formed within the unitary member for uniformly delivering a gas
into a process region. The gas distribution network is formed of an
inlet passage extending upwardly through the upper surface of the
unitary member for connecting to a gas source, a plurality of first
passages converged at a junction and connected with the inlet
passage at the junction, a plurality of second passages connected
with the plurality of first passages, and a plurality of outlet
passages connected with the plurality of second passages for
delivering the gas into a processing region. The first passages
extend radially and outwardly from the junction to the periphery
surface of the unitary member, and the second passages are
non-perpendicular to the first passages and extend outwardly from
the first passages to the periphery surface. The outlet passages
extend downwardly through the lower surface of the unitary member
for delivering the gas into the processing region.
Inventors: |
DeDontney, Jay Brian;
(Prunedale, CA) ; Yao, Jack Chihchieh; (Scotts
Valley, CA) |
Correspondence
Address: |
DORSEY & WHITNEY LLP
555 CALIFORNIA STREET, SUITE 1000
SUITE 1000
SAN FRANCISCO
CA
94104
US
|
Assignee: |
Aviza Technology, Inc.
|
Family ID: |
33511648 |
Appl. No.: |
11/142087 |
Filed: |
May 31, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11142087 |
May 31, 2005 |
|
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10854869 |
May 26, 2004 |
|
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6921437 |
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60475079 |
May 30, 2003 |
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Current U.S.
Class: |
118/715 |
Current CPC
Class: |
C23C 16/45565 20130101;
C23C 16/45574 20130101 |
Class at
Publication: |
118/715 |
International
Class: |
C23C 016/00 |
Claims
We claim:
1. A gas distribution apparatus, comprising: a member having an
upper surface, a lower surface and a periphery surface; and a gas
distribution network formed within said member for uniformly
delivering a gas into a process region, said gas distribution
network being formed of: an inlet passage extending upwardly
through said upper surface for connecting to a gas source; a
plurality of first passages converged at a junction and connected
with said inlet passage at the junction, said first passages extend
radially and outwardly from the junction to the periphery surface;
a plurality of second passages connected with said plurality of
first passages, said second passages are non-perpendicular to said
first passages and extend outwardly from said first passages to the
periphery surface; and a plurality of outlet passages connected
with said plurality of second passages and extending downwardly
through said lower surface for delivering the gas into the
processing region.
2. The apparatus of claim 1 wherein said member is cylindrical
unitary member.
3. The apparatus of claim 1 wherein said plurality of first and
second passages are co-planar.
4. The apparatus of claim 1 wherein said plurality of second
passages between adjacent two passages are in parallel.
5. The apparatus of claim 1 wherein said second passages are angled
from the first passage connected therewith from about 30 to about
45 degree.
6. The apparatus of claim 5 wherein said second passages are angled
from the first passage in about 45 degree.
7. The apparatus of claim 1 wherein said second passages connected
on both sides of a common first passage are staggeredly
arranged.
8. The apparatus of claim 1 wherein said first passages are
comprised of four orthogonal coordinate passages
9. The apparatus of claim 1 wherein said first passages are
comprised of six passages, and adjacent two passages form an angle
of about 60 degree.
10. The apparatus of claim 1 wherein the first passages have a
first diameter, the second passages have a second diameter, and the
outlet passages have an outlet diameter, where the first diameter
is larger than the second diameter, and the second diameter is
larger than the outlet diameter.
11. The apparatus of claim 10 wherein the first diameter is
selected in the range from about 5 to about 15 mm, the second
diameter in the range from about 3 to about 12 mm, and the outlet
diameter in the range from about 0.25 to about 2.5 mm.
12. The apparatus of claim 1 wherein the outlets have a
substantially constant density on the lower surface of the unitary
member.
13. The apparatus of claim 1 wherein the outlet passages are
substantially cylindrical.
14. The apparatus of claim 1 wherein the outlet passages are formed
of a first portion having a smaller diameter and a second portion
having a greater diameter.
15. The apparatus of claim 1 wherein the outlet passages is
provided with threading for receiving inserts to alter the size of
and/or the direction of the gas exiting the outlet passages.
16. A gas distribution apparatus comprising: a plurality of first
passages; and a plurality of second passages coupled to said
plurality of first passages; wherein the first passages are
comprised of four quadrants, and where in two opposite quadrants
the first and second passages are symmetrically arranged and in two
adjacent quadrants the second passages on both sides of a common
first passage are staggeridly arranged.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of and priority to U.S.
Provisional Application No. 60/475,079 filed May 30, 2003, the
disclosure of which is hereby incorporated by reference in its
entirety. This application is a continuation application of U.S.
patent application Ser. No. 10/854,869 filed on May 26, 2004.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the field of
semiconductor equipment and processing. More specifically, the
present invention relates to a gas distribution apparatus useful in
semiconductor fabrication.
BACKGROUND OF THE INVENTION
[0003] Wafer processing reactor systems and methods are widely used
in the manufacture of semiconductors and integrated circuits. One
particular type of wafer processing system utilizes chemical vapor
deposition (CVD) to deposit films or layers on the surface of a
substrate as a step in the manufacture of semiconductors and
integrated circuits. In CVD processes that require multiple gases,
the gases are generally combined within a mixing chamber. The
gaseous mixture is then coupled through a conduit to a distribution
plate or showerhead, which contains a plurality of holes such that
the gaseous mixture is evenly distributed into a process region. As
the gaseous mixture enters the process region and is infused with
energy such as being heated, a chemical reaction occurs between the
gases to form a film on a substrate proximate the processing
region.
[0004] Although it is generally advantageous to mix gases prior to
delivery into a process region to ensure that the gases are
uniformly distributed into the process region, gases tend to begin
reacting within the mixing chamber. Consequently, deposition or
etching of the mixing chamber, conduits and other chamber
components may occur prior to the gaseous mixture reaching the
process region. Additionally, reaction by-products and deposits may
accumulate in the chamber gas delivery components.
[0005] Some semiconductor processes require delivery of gases into
a process region in a sequential manner without premixing. For
example, in an atomic layer deposition (ALD) process, which
increasingly becomes an alternative to CVD processes, each reactant
gas is independently introduced into a reaction chamber through,
for example, a showerhead, so that no gas phase intermixing occurs.
A monolayer of a first reactant is physi- or chemi-sorbed onto a
substrate surface. After the excess first reactant is evacuated
from the reaction chamber, a second reactant is then introduced
through the showerhead to the reaction chamber and reacts with the
first reactant to form a monolayer of the desired film via a
self-limiting surface reaction. A desired film thickness is
obtained by repeating the deposition cycle as necessary. It is
advantageous to introduce the first and second reactants
independently and separately through the showerhead to avoid any
reaction between the reactants in the showerhead.
[0006] Therefore, in either a CVD or an ALD process, it is desired
to maintain gases in separate passageways within a showerhead until
they exit the showerhead into a process region.
[0007] To distribute process gases from a single inlet port to a
multitude of outlet holes, gas distribution networks created in a
showerhead body may be used. For example, a plurality of parallel
channels can be formed in a unitary showerhead body from which a
multitude of perpendicular outlet channels deliver process
chemicals into a process region. The parallel channels are
intersected perpendicularly by a single transverse plenum connected
to a central gas source inlet line. Process gas passes from the
inlet to the outlets of the showerhead by following a "Cartesian"
path by flowing laterally along the transverse plenum, transverse
through the parallel channels, and the outlet channels into the
process region.
[0008] A disadvantage of this design is that there is a large
variation in total flow path to reach points of constant radius
within the showerhead. As a result, there is typical a large
variation in backpressure within the interior flow channels that
result in an unacceptable azimuthal and radial variation in outlet
gas flow velocity from the multitude of outlet holes. Furthermore,
in showerhead designs with a single central gas inlet, there exists
an unavoidable time lag between the gases that exist near the
center of the showerhead and those existing at the outer perimeter.
The large variation in total flow path at points of constant radius
inherent with Cartesian-style flow networks creates a "phase error"
that may lead to non-uniform chemical concentrations around the
perimeter of the showerhead which may affect deposition in
transient-flow processes.
[0009] To minimize the azimuthal variation in time-lag, radially
oriented channels that converge at the center gas inlet may be
employed instead of a multitude of parallel channels. However, this
type of design leads to a decreasing outlet hole density (hole per
square centimeter) due to the divergence of the radial passages.
This may be compensated somewhat by additional radial passages at
larger radii, however, these require cross-connection to the same
source of gas which becomes difficult to do in a truly unit body
block of material. Furthermore, it is not apparent that this will
yield acceptable flow uniformity either.
[0010] Therefore, there is a need of a gas distribution system that
provides improved uniform outlet velocity distribution and reduced
variation in azimuthal time lag between the gases that exit near
the center of the showerhead and those existing at the outer
perimeter. Further developments in gas distribution apparatus
useful in CVD and ALD processes are needed.
SUMMARY OF THE INVENTION
[0011] A gas distribution apparatus useful in semiconductor
fabrication is provided. The gas distribution apparatus promotes
uniformly delivery of gases into a process region and reduces
azimuthal variation in time lag between gas that exits near the
center and gas exiting at the outer perimeter of the apparatus.
[0012] In one embodiment, the present gas distribution apparatus
comprises a member and a gas distribution network formed within the
unitary member for uniformly delivering a gas into a process
region. The member can be a unitary member. The gas distribution
network is formed of an inlet passage extending upwardly through
the upper surface of the unitary member for connecting to a gas
source. A plurality of first passages converge at a junction and
interconnect with the inlet passage at the junction. A plurality of
second passages are connected with the plurality of first passages,
and a plurality of outlet passages are connected with the plurality
of second passages for delivering the gas into a processing region.
The first passages extend radially and outwardly from the junction
to the periphery surface of the unitary member. The second passages
are non-perpendicular to the first passages and extend outwardly
from the first passages to the periphery surface. The outlet
passages extend downwardly through the lower surface of the unitary
member for delivering the gas into the processing region.
[0013] In one embodiment, the first passages are comprised of four
orthogonal coordinate passages dividing the gas distribution
network into four regions or quadrants. The second passages in each
of the quadrants are parallel with each other. In opposite two
quadrants, the first and second passages are symmetrically
arranged. In adjacent two quadrants, the second passages on both
sides of a common first passage are staggeredly arranged. The first
and second passages constitute an angle from about 30 to about 45.
In one embodiment, the angle is about 45 degrees.
[0014] In another embodiment, the first passages are comprised of
six passages, and adjacent two passages form an angle of about 60
degrees.
[0015] Generally, the first passages have a diameter larger than
the diameter of the second passages. The second passages have a
diameter larger than the diameter of the outlet passages. In one
embodiment, the diameter of the first passages is in the range from
about 5 to about 15 mm, the diameter of the second passages is in
the range from about 3 to about 12 mm, and the outlet diameter is
in the range from about 0.25 to about 2.5 mm.
[0016] In another embodiment, the outlet passages are substantially
cylindrical and adapted to receive inserts to alter the size of
and/or direction of gases exiting the outlets into a process
region. In a further embodiment, the outlet passages are provided
with threads for receiving the inserts.
[0017] In one embodiment, the present gas distribution system
comprises a unitary cylindrical member and two independent gas
distribution networks formed within the unitary member. Each of the
gas distribution networks is formed of an inlet passage extending
upwardly through the upper surface of the unitary member for
connecting to a gas source, a plurality of co-planar first passages
converged at a junction and interconnected with the inlet passage
at the junction, a plurality of second passages connected with the
plurality of first passages, and a plurality of outlet passages
connected with the plurality of second passages and extending
downwardly through the lower surface of the unitary member for
delivering the gas into the processing region. The first passages
extend radially and outwardly from the junction to the periphery
surface of the unitary member. The second passages are co-planar
with and non-perpendicular to the first passages and extend
outwardly from the first passages to the periphery surface. The
first and second passages of each of the gas distribution networks
are formed at different elevations within the unitary member and
the inlet passages of each of the gas distribution networks offset
each other. The two independent gas distribution networks are not
in fluid communication within the unitary member. In one
embodiment, the first passages of each of the gas distribution
networks are comprised of four orthogonal coordinate passages. In
another embodiment, the outlet passages of each of the two gas
distribution networks extend through the lower surface in an
alternate and even configuration. In a further embodiment, the two
gas distribution networks have substantially the same dimensions
and configurations.
[0018] In one embedment, the present gas distribution system
comprises a unitary cylindrical member having an upper surface, a
lower surface and a periphery surface, and three independent gas
distribution networks formed within the unitary member. Each of the
gas distribution networks is formed of an inlet passage, a
plurality of first passages, a plurality of second passages
connected with the first passages, and a plurality of outlet
passages connected with the second passages. The inlet passage
extends upwardly through the upper surface for connecting to a gas
source. The first passages converge at a junction and is
interconnected with the inlet passage at the junction. The first
passages extend radially and outwardly from the junction to the
periphery surface. The second passages are co-planar with and
non-perpendicular to the first passages and extend outwardly from
the first passages to the periphery surface. The outlet passages
are connected with the second passages and extend downwardly
through the lower surface for delivering the gas into the
processing region. The first and second passages of each of the
three gas distribution networks are formed at different elevations
within the unitary member and the inlet passages of each of the
three gas distribution networks offset each other. The three
independent gas distribution networks are not in fluid
communication within the unitary member. In one embodiment, the
first passages of each of the three gas distribution networks are
comprised of six passages, and adjacent two passages form an angle
of about 60 degrees. The three gas distribution networks may have
substantially the same dimensions and configurations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Other objects and advantages of the present invention become
apparent upon reading of the detailed description of the invention
provided below and upon reference to the drawings in which:
[0020] FIG. 1 is a schematic view of a semiconductor reactor system
including a gas distribution apparatus in accordance with one
embodiment of the present invention.
[0021] FIG. 2 is an external view of a gas distribution apparatus
machined from a unitary member in accordance with one embodiment of
the present invention.
[0022] FIG. 3 shows an internal gas distribution network formed
within a unitary member in accordance with one embodiment of the
present invention.
[0023] FIG. 4 is an external view of a gas distribution apparatus
showing outlet passages through the bottom surface of a unitary
member in accordance with one embodiment of the invention.
[0024] FIG. 5 is a bubble plot showing outlet velocities in the
geometry of a prior art showerhead.
[0025] FIG. 6 is a bubble plot showing outlet velocities in the
geometry of a gas distribution apparatus in accordance with one
embodiment of the present invention.
[0026] FIG. 7 is a plot showing internal and external path length
ratios in a prior art showerhead.
[0027] FIG. 8 is a plot showing internal and external path length
ratios in a gas distribution apparatus in accordance with one
embodiment of the present invention.
[0028] FIG. 9 shows two internal gas distribution networks formed
within a unitary member in accordance with one embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0029] A gas distribution apparatus useful in semiconductor
fabrication is provided. In general, the gas distribution apparatus
of the present invention comprises a unitary member and one or more
gas distribution networks formed within the unitary member for
uniformly delivering gases into a process region.
[0030] Referring to the drawings where like components are
designated by like reference numerals, the present gas distribution
apparatus is described in more detail.
[0031] FIG. 1 schematically shows a semiconductor wafer processing
reaction chamber 10, for example, an atomic layer deposition (ALD)
reactor or a CVD reactor that includes a showerhead 12 of the
present invention. It should be noted that the reactor 10 shown in
FIG. 1 is for illustrative purpose only and not intended to limit
the scope of the invention in any way. The showerhead described
below can be used in any other system where uniform gas
distribution into a process region is desired. The reactor 10
includes an enclosure 14 defining a processing region 16. A
substrate 18, such as a semiconductor wafer, is maintained
proximate the process region 16 on a pedestal 20. The pedestal 20
moves vertically within the enclosure 14 to a position that allows
the substrate 18 to be removed. While in the lowered position, a
new substrate 18 is placed on the pedestal 20. The pedestal 20 is
then raised into a process position, which places the substrate
proximate the process region 16. Process gases are supplied through
the showerhead 12. The showerhead 12 forms a lid of the reactor 10.
In one embodiment of the present invention, for example, in a CVD
process, two gases (Gas 1 and 2) are independently and separately
supplied to the showerhead 12. The two gases are distributed to the
process region 16 via two separate gas distribution networks 21
formed in the showerhead 12. These gases react and form a deposit
on the substrate 18. In another embodiment of the present
invention, for example, in an ALD process, a first reactant gas
(Gas 1) is introduced into the process region 16 via a gas
distribution network formed within the showerhead 12. After a
monolayer of a first reactant gas is physi- or chemi-sorbed onto
the substrate surface, the excess first reactant gas is evacuated
from the reaction chamber 10 with the aid of an inert purge gas. A
second reactant (Gas 2) is then introduced to the process region 16
via a separate gas distribution network formed within the
showerhead. The second reactant gas reacts with the first reactant
forming a monolayer of the desired film via a self-limiting surface
reaction. The excess second reactant is then evacuated with the aid
of an inert purge gas. A desired film thickness is obtained by
repeating the deposition cycle as necessary.
[0032] The showerhead 12 is preferably a unitary member 13, as
shown in FIG. 2, and has one or more gas distribution networks 21,
as shown in FIG. 3, formed within the unitary member 13. Member 13
can also be two or more blocks combined together. To simplify
description of the invention, a single gas port 22 and a single gas
distribution network 21 are shown in FIGS. 2 and 3. It should be
noted that two or three gas distribution networks 21 can be
independently formed at different elevations within the unitary
member 13, and two or three gas ports 22 can be provided to
independently and separately supply gases into the two or three gas
distribution networks 21. The two or three gas distribution
networks 21 are not interconnected within the unitary member 13 so
that two or three gases are independently and separately introduced
into a process region 16 without premixing. In one embodiment where
two or three gas distribution networks 21 are formed within the
unitary member 13, two or three gases can be simultaneously
supplied into the showerhead 12 from separate gas sources (not
shown). Since the two or three gas distribution networks 21 are not
in fluid communication with each other within the unitary member
13, the two or three gases are not mixed until they exit the
showerhead 12 into the process region 16. Alternatively, two or
three gases are supplied into the process region 16 sequentially
via the two or three gas distribution networks 21 within the
unitary member 13 to meet specific process requirements, for
example, in an atomic layer deposition process.
[0033] Member 13 is preferably machined from a block of aluminum,
stainless steel, nickel-based alloys, or any material that does not
react with the particular gases being supplied into the showerhead
12. The unitary member 13 can be in a cylindrical shape or any
shape suitable as a lid for the reactor 10. The unitary member 13
comprises an upper surface 23, a lower surface 24, and a peripheral
surface 25. A plurality of channels, passages or holes are formed
within the unitary member 13 to form a gas distribution network 21.
Various manufacturing techniques known in the art can be used to
form the channels, passages or holes, such as electric discharge
drilling, mechanical drilling, pressurized reactant drilling, water
jet cutting, and the like. In one embodiment, these channels or
passages are formed by mechanical drilling and/or an electrode
discharge machine (EDM).
[0034] FIG. 3 shows a gas distribution network 21 formed within the
unitary member 13. For clarity, only channels, passages, or holes
forming the gas distribution network 21 are shown in FIG. 3. The
remaining solid materials that define these channels, passages or
holes of the gas distribution network 21 are not shown in FIG.
3.
[0035] As illustrated in FIG. 3, the gas distribution network 21
comprises an inlet passage 26. The inlet passage 26 is coupled to a
gas source (not shown) via a conduit (not shown) for supplying a
gas into the gas distribution network 21. The inlet 26 extends
upwardly and through the upper surface 23.
[0036] A plurality of horizontal passages or plenums 28a-d are
formed within the unitary member 13. The horizontal plenums 28a-d
are converged at a junction 30 and extend radially and outwardly to
the peripheral surface 25 of the unitary member 13. The horizontal
plenums 28a-d are closed at the peripheral surface 25. The
horizontal plenums 28a-d can be formed by drilling from the
peripheral surface 25. The openings on the peripheral surface 25
are closed by for example sealing plugs (not shown) after the
plenums 28a-d are formed. The inlet passage 26 is connected with
the plenums 28a-d via the junction 30. In FIG. 3, four orthogonal
coordinate plenums 28a-d are shown for illustrative purpose. It
should be noted that other number of plenums can be formed. For
example, six plenums can be formed converging at a junction, and
adjacent two plenums constitute an angle of 60 degrees. A gas is
introduced via the inlet passage 26 and distributed into the
horizontal plenums 28a-d.
[0037] A plurality of branch passages or tributaries 32 are formed
along the path of each of the horizontal plenums 28a-d. The
tributaries 32 extend from the plenum 28 to the peripheral surface
25 of the unitary member 13. The tributaries 32 are closed at the
peripheral surface 25. These branch passages or tributaries 32 are
formed at a same elevation with the plenums 28. In one embodiment,
such as shown in FIG. 3, the gas distribution network 21 is divided
into four regions or quadrants 34a-d by four orthogonal coordinate
plenums 28a-d. An array of parallel tributaries 32 are formed in
each of the quadrants 34a-d. The length of each of individual
tributary 32 is determined to define a desired gas distribution
configuration. In one embodiment where a substantially circular
distribution configuration is desired, each individual tributary 32
extends outwardly and closed at a location that is substantially
equally distant from the peripheral surface 25 of the cylindrical
member 13. Other distribution configurations such as a square
pattern can be defined by varying the length of the plenums 28a-d,
tributaries 32, and outlets 36 described below.
[0038] In opposite two quadrants such as 34a and 34c, or 34b and
34d, the configuration of tributaries 32 are symmetrical. In
adjacent two quadrants such as 34a and 34b, or 34a and 34c, the
tributaries 32 formed along a common plenum such as 28a or 28b are
staggered and angled from the plenum. In one embodiment, each
tributary 32 forms an acute angle with the plenum 28 of about 45
degrees. This angle can be determined by the geometrical
requirements imposed by the number of gas distribution networks and
the desired outlet hole patterns.
[0039] Along the path of each of the tributaries 32, an array of
passages or outlets 36 are formed for distributing gases into a
process region 16. The outlets 36 extends downwardly and through
the lower surface 24 of the unitary member 13 as shown in FIG. 4.
The passages of the outlets 36 can be straight and cylindrical.
Alternatively, the passages of the outlets 36 comprise a first
portion proximate the tributary 32 and a second portion distant the
tributary 32. The first portion of the outlet passage may have a
larger or smaller diameter than that of the second portion to
control the back pressure of the outlets 36 according to process
requirements. The outlet passages may also be provided with threads
for receiving inserts that are designed to alter the size of the
outlet or direction of gases exiting the outlet into the process
region. U.S. application Ser. No. ______ (Attorney Docket No.
A-72314) entitled "Adjustable Gas Distribution System" filed
concurrently with this application discloses embodiments of inserts
that can be used in the present gas distribution system, the
disclosure of which is hereby incorporated by reference in its
entirety.
[0040] The diameters of the plenums 28a-d, tributaries 32, and
outlets 36 are selected to provide a desired outlet velocity. In
one embodiment, the diameters of the plenums 28a-d are larger than
those of the tributaries 32, and the diameters of the tributaries
32 are larger than those of the outlets 36. Small outlet diameters
create resistance to gas flow so as to sustain smaller variation in
back pressure among all of the outlets. Large plenum and tributary
diameters assist in this effect which is desirable. Typically, if
the backing pressure is uniform among all the outlets, the outlet
velocities are also uniform. However, it is desirable not to make
the outlets too small as this may lead to "jetting" of gases, which
is undesirable in semiconductor processes. The diameters of the
outlets 36 can be uniform throughout the entire distribution
region. Alternatively, the diameters of the outlets 32 differ to
provide an inner region with a larger diameters and an outer region
with smaller diameters.
[0041] In one embodiment, the diameter of the plenums 28a-d is
selected in the range from about 5 mm to about 15 mm, the diameter
of the tributaries 32 in the range from about 3 mm to about 12 mm,
and the diameter of the outlets 36 in the range from about 0.25 mm
to about 2.5 mm. In another embodiment, the diameter of the plenums
28a-d is selected in the range from about 9 mm to about 12 mm, the
diameter of the tributaries 32 in the range from about 6 mm to
about 9 mm, and the diameter of the outlets 36 in the range from
about 1 mm to about 1.5 mm.
[0042] For clarity and simplicity, only some tributaries, outlets
and plenums are shown in FIG. 3 for illustrative purpose. It should
be noted that numerous tributaries and outlets can be formed to
provide desired outlet density for specific processes. For example,
the number of plenums, tributaries and outlets are selected to
provide an outlet density of about 1 hole per 2 square
centimeters.
[0043] Table 1 summarizes the modeling results for the present gas
distribution system as analyzed in computational fluid dynamics
(CFD) simulations.
1TABLE 1 Plenum Tributary Outlet Diameter Diameter Diameter Range/
Max/ Design No. (mm) (mm) (mm) Average Min 1 10.0 8.0 1.5 0.131
1.138 2 10.0 8.0 1.5 0.133 1.140 3 8.0 8.0 1.5 0.203 1.220 4 9.0
6.0 1.5 0.268 1.287 5 8.0 8.0 1.5 0.290 1.328 6 10.0 6.0 1.5 0.337
1.364
[0044] In Table 1, Max/Min refers to the ratio of maximum to
minimum outlet velocity. Range/Average refers to the ratio of
Max/Min value to the average gas flow velocity. The values of
Max/Min and Range/Average are used to rank the performance of the
gas distribution systems. Small values of Max/Min and Range/Average
are desired for uniform distribution of gases into a process
region.
[0045] Table 1 demonstrates a much better performance of the
present gas distribution apparatus over prior art showerheads. In a
prior art showerhead of the Cartesian style network type, the
Max/Min ratio was tested and found to be 3.584, which means that
the variation of the outlet velocity is as high as more than 350%,
and the Range/Average was 1.50, or 150%. In comparison, the Max/Min
ratios for the gas distribution system of the present invention
range only from 1.220 to 1.364, and the Range/Average ratios range
only from 0.131 to 0.337.
[0046] FIG. 5 is a bubble plot that shows the outlet velocities in
the geometry of a prior art showerhead. FIG. 6 is a bubble plot
that shows the outlet velocities in the geometry of the present gas
distribution system as defined by design 5 in Table 1. As shown in
FIG. 5, the bubbles in the outer perimeter regions are obviously
smaller than those in the inner region. In other words, the flow
velocities in the inner region are greater than those in the outer
perimeter region. FIG. 6 shows an improvement of the flow velocity
provided by the gas distribution system of the present invention.
FIG. 6 demonstrates a substantially uniform outlet velocities
regardless of the distance from the center region.
[0047] One advantage of the present gas distribution system is a
smaller transit time variation in the polar directions over that of
the prior art showerhead design. FIGS. 7 and 8 compare the internal
and external path length in the present gas distribution system and
prior art showerhead. In FIGS. 7 and 8, x-axis represents outlet
perimeter positions, and y-axis represents the length ratio of an
internal path for a gas traveling to an outlet at the outer
parameter and an external path that the gas would travel from the
center junction radially and outwardly towards that same outlet. In
the present gas distribution system illustrated in FIG. 3, the
internal/external path ratio at perimeter positions G and H is
close to 1 due to the radial design, as shown in FIG. 8. In a prior
art showerhead, the internal/external path ratio at a equivalent
perimeter positions can be as high as 1.4, as shown in FIG. 7.
FIGS. 7 and 8 demonstrate that the present gas distribution system
greatly reduces the azimuthal variation in time lag between gases
that exit near the center of the showerhead and those exiting at
the outer perimeter. This in turn enhances gas distribution
uniformity into a process region, which is desirable in
semiconductor manufacturing.
[0048] In one embodiment, two internal gas distribution networks
are formed at different elevations within a unitary member to
independently and separately supply two gases into a process
region. Each of the two internal gas distribution networks is
described above with reference to FIGS. 2-8. The two internal gas
distribution networks are not in fluid communication within the
unitary member. The configuration of the two internal gas
distribution networks can be substantially the same. In one
embodiment as shown in FIG. 9, each of the two internal gas
distribution networks is divided into four regions or quadrants by
four orthogonal coordinate main passages or plenums 54a-d and
64a-d. The four plenums converge at a junction and extend radially
and outwardly to the peripheral surface of the unitary member. A
plurality of parallel branch passages or tributaries 58 and 68 are
formed in each of the quadrants. The tributaries 58 and 68 are
coupled to the plenums 54a-d and 64a-d respectively and extend
outwardly to the peripheral surface of the unitary member. The
tributaries and the plenum connected therewith constitute an angle
about 45 degrees. An inlet passage is formed and coupled to the
junction of the plenums. The inlet passage extends upwardly and
through the upper surface of the unitary member to couple to a gas
source via a conduit. A plurality of vertical outlet passages 59
and 69 are formed along the path of each of the tributaries 58 and
68 respectively. The outlet passages 59 and 69 extend downwardly
and through the lower surface of the unitary member for directing
gases into a process region.
[0049] The two internal gas distribution networks are arranged at
different elevations within the unitary member in such a manner so
that the plenums, tributaries, inlet and outlet passages of one
internal gas distribution network offset corresponding plenums,
tributaries, inlet and outlet passages of another internal gas
distribution network. In other words, the corresponding plenums,
tributaries, and inlet and outlet passages are not overlapped when
viewed from the top or bottom of the unitary member. When viewed
from the bottom of the unitary member, the outlet passages of each
of the internal gas distribution networks extend through the bottom
surface in an alternative and even configuration.
[0050] In a further embodiment, three internal gas distribution
networks are formed at different elevations within a unitary member
to independently and separately supply three gases into a process
region. Each of the three internal gas distribution networks is
described above with reference to FIGS. 2-8. The three internal gas
distribution networks are not in fluid communication within the
unitary member. The configuration of the three internal gas
distribution networks can be substantially the same. In one
embodiment, each of the three internal gas distribution networks is
divided into six regions by six main passages or plenums. The six
plenums converge at a junction and extend radially and outwardly to
the peripheral surface of the unitary member. A plurality of
parallel branch passages or tributaries are formed in each of the
six regions. The tributaries are coupled to the plenums and extend
outwardly to the peripheral surface of the unitary member. The
tributaries and the plenum connected therewith constitute an angle
about 30 degrees. An inlet passage is formed and coupled to the
junction of the plenums. The inlet passage extends upwardly and
through the upper surface of the unitary member to couple to a gas
source via a conduit. A plurality of vertical outlet passages are
formed along the path of each of the tributaries. The outlet
passages extend downwardly and through the lower surface of the
unitary member for directing gases into a process region.
[0051] The three internal gas distribution networks are arranged at
different elevations within the unitary member in such a manner so
that the inlet and outlet passages of one internal gas distribution
network offset the inlet and outlet passages of the other two
internal gas distribution network. In other words, the
corresponding inlet and out passages are not overlapped when viewed
from the top or bottom of the unitary member.
[0052] As described above, a gas distribution apparatus has been
provided by the present invention. The foregoing description of
specific embodiments of the invention have been presented for the
purpose of illustration and description. They are not intended to
be exhaustive or to limit the invention to the precise forms
disclosed, and obviously many modifications, embodiments, and
variations are possible in light of the above teaching. It is
intended that the scope of the invention be defined by the claims
appended hereto and their equivalents.
* * * * *