U.S. patent application number 11/348595 was filed with the patent office on 2006-06-15 for method and apparatus for silicon oxide deposition on large area substrates.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Wendell T. Blonigan, Quanyuan Shang, Sanjay D. Yadav.
Application Number | 20060127068 11/348595 |
Document ID | / |
Family ID | 33097841 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060127068 |
Kind Code |
A1 |
Yadav; Sanjay D. ; et
al. |
June 15, 2006 |
Method and apparatus for silicon oxide deposition on large area
substrates
Abstract
A method and apparatus for depositing a dielectric material at a
rate of at least 3000 Angstroms per minute on a large area
substrate that has a surface area of at least about 0.35 square
meters is provided. In one embodiment, the dielectric material is
silicon oxide. Also provided is a large area substrate having a
layer of dielectric material deposited by a process yielding a
deposition rate in excess of about 3000 Angstroms per minute and a
processing chamber for fabricating the same.
Inventors: |
Yadav; Sanjay D.; (San Jose,
CA) ; Shang; Quanyuan; (Saratoga, CA) ;
Blonigan; Wendell T.; (Union City, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
33097841 |
Appl. No.: |
11/348595 |
Filed: |
February 7, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10409466 |
Apr 7, 2003 |
7031600 |
|
|
11348595 |
Feb 7, 2006 |
|
|
|
Current U.S.
Class: |
392/416 ;
392/418 |
Current CPC
Class: |
C23C 16/402 20130101;
C23C 16/4485 20130101 |
Class at
Publication: |
392/416 ;
392/418 |
International
Class: |
A21B 2/00 20060101
A21B002/00 |
Claims
1. A method for depositing a dielectric material on a large area
substrate, comprising: placing a substrate having a surface area of
at least 0.357 square meters on a substrate support assembly inside
a processing chamber; heating the substrate; flowing at least one
precursor gas into the processing chamber at a rate greater than
about 730 sccm; and forming a plasma from at least the precursor
gas within the processing chamber; and depositing a dielectric
material at a rate greater than about 3000 to at least about 4,000
Angstroms per minute.
2. The method of claim 1, wherein the step of heating the substrate
further comprises: heating the substrate between about 350 to about
440 degrees Celsius.
3. The method of claim 1, wherein the step of depositing a
dielectric material further comprises: depositing silicon
oxide.
4. The method of claim 1, wherein the step of flowing at least one
precursor gas further comprises: flowing a TEOS into a vaporizer
coupled to the processing chamber; and heating the vaporizer to a
temperature between about 90 to about 150 degrees Celsius to
generate the precursor gas. flowing a resultant vapor into the
processing chamber.
5. The method of claim 4, wherein the flow rate of the precursor
gas is in the range of from about 20 to about 100 grams per
minute.
6. The method of claim 4, wherein the flow rate of the precursor
gas is at least about 2,320 sccm.
7. The method of claim 4 further comprising: maintaining the
precursor gas disposed between the vaporizer and chamber at a
temperature above about 90 degrees Celsius.
8. The method of claim 7, wherein the precursor gas disposed
between the vaporizer and processing chamber is about 90 to about
150 degrees Celsius.
9. The method of claim 4 further comprising: mixing helium with
TEOS prior to entering the vaporizer.
10. The method of claim 1, wherein the step of forming a plasma
further comprises: applying about 5,000 Watts RF to energize the
precursor gas.
11. The method of claim 2, wherein the dielectric material is
deposited at a rate of at least about 3500 to at least about 14,000
Angstroms per minute.
12. The method of claim 11, wherein the step of flowing at least
one precursor gas further comprises: combining the precursor gas
with oxygen.
13. The method of claim 12, wherein the oxygen combined with the
precursor gas is supplied at a rate of about 2,000 to about 15,000
sccm.
14. A method for depositing a layer of silicon oxide on a large
area substrate, comprising: flowing TEOS at a rate of at least
about 20 grams per minute through a vaporizer coupled to a
processing chamber to generate a precursor gas; mixing oxygen with
the precursor gas to form a gas mixture; forming a plasma from the
gas mixture within the processing chamber; and depositing silicon
oxide on the substrate at a rate of at least 3000 Angstroms per
minute.
15. The method of claim 14 further comprising: placing the
substrate having a surface area greater than about 0.35 square
meters on a substrate support assembly inside the processing
chamber; heating the substrate to a temperature between about 350
to about 440 degrees Celsius; and flowing TEOS at a rate of at
least about 20 to about 100 grams per minute through the
vaporizer.
16. The method of claim 14 further comprising: placing the
substrate in the processing chamber, wherein the processing chamber
has an internal volume greater than or equal to about 380
liters.
17. A large area substrate having a layer of silicon oxide
deposited thereon by a method comprising: placing a substrate on a
substrate support assembly inside a processing chamber adapted to
process large area substrates; heating the substrate; flowing at
least one precursor gas into the processing chamber at a rate
greater than about 20 grams per minute; and forming a plasma from
at least the precursor gas within the processing chamber; and
depositing a dielectric material over about at least 0.357 square
meters of the substrate at a rate greater than 3000 Angstroms per
minute.
18. A large area substrate having a silicon oxide layer deposited
by the method comprising: placing a substrate in a processing
chamber having an internal volume greater than or equal to about
380 liters; flowing TEOS into the processing chamber at a rate of
at least about 20 grams per minute; forming a plasma within the
processing chamber; and depositing silicon oxide on the substrate
at a rate of at least 3500 Angstroms per minute.
19. A processing system, comprising: a processing chamber; a
process gas source; a housing; a temperature controlled mass flow
meter disposed in the housing and coupled to the gas source; a
vaporizer disposed in the housing and coupled between the mass flow
meter and the processing chamber; and a thermally insulating member
disposed in the housing between the vaporizer and the mass flow
meter.
20. An apparatus for depositing a layer of silicon oxide on a large
area substrate comprising: a processing chamber having a processing
volume greater than or equal to about 380 liters; a gas
distribution plate coupled to a lid of the processing chamber; a
substrate support disposed within the processing chamber below the
gas distribution plate; at least one heating element embedded
within the substrate support; a vaporizer coupled to the processing
chamber and adapted to provide at least about 20 grams per minute
of TEOS vapor to the processing chamber; and a power source coupled
to the gas distribution plate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of co-pending
U.S. patent application Ser. No. 10/409,466, filed Apr. 7, 2003,
which is incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the invention generally relate to a method
and apparatus for silicon oxide deposition on large area
substrates.
[0004] 2. Background of the Related Art
[0005] Thin film transistors (TFTs) are conventionally made on
large area glass substrates or plates for use in monitors, flat
panel displays, solar cells, personal digital assistants (PDAs),
cell phones and the like. Many TFT manufacturers utilize large area
substrates for TFT fabrication with dimensions exceeding 550 mm by
650 mm, with a demand for even larger sizes. It is envisioned that
these dimensions may exceed 4.0 square meters in the near
future.
[0006] TFTs are made in a cluster tool by sequential deposition of
various films including amorphous silicon, doped and undoped
silicon oxides, silicon nitride and the like in vacuum chambers
typically disposed around a central transfer chamber. TFTs
generally comprise two glass plates having a layer of liquid
crystal material sandwiched therebetween. At least one of the glass
plates includes at least one conductive film disposed thereon that
is coupled to a power supply. Power supplied to the conductive film
from the power supply changes the orientation of the liquid crystal
material, creating a pattern such as text or graphics seen on the
display. One fabrication process frequently used to produce flat
panels is plasma enhanced chemical vapor deposition (PECVD).
[0007] Plasma enhanced chemical vapor deposition is generally
employed to deposit thin films on a substrate such as a flat panel
or semiconductor wafer. Plasma enhanced chemical vapor deposition
is generally accomplished by introducing a precursor gas into a
vacuum chamber that contains a substrate. The precursor gas is
typically directed through a distribution plate situated near the
top of the chamber. The precursor gas in the chamber is energized
(e.g., excited) to form a plasma by applying RF power to the
chamber from one or more RF sources coupled to the chamber. The
excited gas reacts to form a layer of material on a surface of the
substrate that is positioned on a temperature controlled substrate
support. In applications where the substrate receives a layer of
low temperature polysilicon, the substrate support may be heated in
excess of 400 degrees Celsius. Volatile by-products produced during
the reaction are pumped from the chamber through an exhaust
system.
[0008] One of the obstacles in depositing films, particularly
silicon oxides formed from TEOS precursors, is the long time
required to deposit a predetermined thickness of film on the
surface of larger size substrates. In particular, deposition rates
slow exponentially as process gases cannot be provided to the
chamber at a rate that allows commercially practical deposition
rates. For example, conventional vaporizers utilized to convert
liquid TEOS into TEOS vapor suitable for CVD processes are limited
to about 10 g/m and correspondingly limit deposition rates to about
1500 to about a maximum of 2500 .ANG./m in typical processes. The
lack of generators suitable for providing high volumetric flows of
process gases (i.e., flows in excess of 15 g/m) is a major obstacle
for commercially practical silicon oxide deposition on next
generation size large area substrates.
[0009] Further, TEOS vaporizers, such as conventional TEOS bubblers
utilized in many large area substrate CVD applications, also tend
to generate and entrain liquid droplets at their upper end of
operation, which is generally limited to about 10 g/m. Droplets
entering the processing chamber may contaminate the substrate
and/or result in process variation. As the size of large area
substrates commands a substantial investment in material and
processing costs, excessive defects due to droplets or inadequate
precursor gas generation are unacceptable. Moreover, droplets
entrained in the gases entering the processing chamber result in
prolonged vacuum pump-down time. For example, conventional large
area substrate CVD systems encounter pump-down times of about 23-30
seconds for conventional vaporizers producing 5 g/min TEOS and
about 30-34 seconds for conventional vaporizers producing 10 g/min
TEOS. Minimization of the pump-down time is highly desirable as it
would directly result in increased substrate throughput.
[0010] Therefore, is a need for a method and apparatus for
generating TEOS vapor (among other precursors or process gases) for
depositing dielectric material at a rate of at least 2,000 .ANG./m
on large area substrates.
SUMMARY OF THE INVENTION
[0011] A method and apparatus for depositing a dielectric material
at a rate of at least 3000 Angstroms per minute on a large area
substrate that has a surface area of at least about 0.35 square
meters is provided. In one embodiment, the dielectric material is
silicon oxide. Also provided is a large area substrate having a
layer of dielectric material deposited by a process yielding a
deposition rate in excess of about 3000 Angstroms per minute and a
processing chamber for fabricating the same.
[0012] In another aspect of the invention, a vaporizer module
suitable for use in semiconductor processing is provided. In one
embodiment, includes a first thermally conductive plate having a
thickness of at least 0.125 disposed against a second plate
thermally conductive plate to define a vaporizer assembly. A
plurality of grooves are formed at least partially in the first
plate and covered by the second plate. A first port and a second
port are formed in respective ends of the vaporizer assembly and
fluidly coupled by the grooves.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] A more particular description of the invention, briefly
summarized above, may be had by reference to the embodiments
thereof that are illustrated in the appended drawings. It is to be
noted, however, that the appended drawings illustrate only typical
embodiments of this invention and are therefore not to be
considered limiting of its scope, for the invention may admit to
other equally effective embodiments.
[0014] FIG. 1 is a sectional view of an exemplary large area
substrate processing system including one embodiment of a vaporizer
module of the present invention;
[0015] FIG. 2 depicts a sectional view of the processing chamber of
FIG. 1 including one embodiment of the vaporizer module of the
present invention;
[0016] FIG. 3A is a sectional view of one embodiment of a vaporizer
module of the present invention;
[0017] FIG. 3B is a sectional view of the vaporizer included in the
vaporizer module of FIG. 3A; and
[0018] FIG. 4 depicts a flow diagram of one embodiment of a process
in which the vaporizer module of FIG. 3A may be utilized.
[0019] To facilitate understanding, identical reference numerals
have been used, wherever possible, to designate identical elements
that are common to the figures.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] FIG. 1 is a top sectional view of one embodiment of a plasma
enhanced chemical vapor deposition system 100 adapted to deposit
dielectric material on large area substrates at a rate in excess of
3000 and up to and exceeding 14,000 angstroms per minute.
Typically, large area substrates have a surface area (on one side)
greater than or equal to about 0.35 square meters. The system 100
generally includes a central transfer chamber 102 having a
plurality of processing chambers 104 coupled thereto. Optionally,
one of the processing chambers 104 may be a heating chamber 104'.
At least one load lock chamber 106 is coupled between the transfer
chamber 102 and a factory interface 108 to facilitate transfer of
substrates 140 between the factory interface 108 and the processing
chambers 104 (two are shown). The system 100 also includes an
interface robot 110 disposed in the factory interface 108 and a
transfer robot 112 disposed in the transfer chamber 102 to enable
substrate movement through the load lock chambers 106 and around
the system 100. One large area substrate processing system that may
be adapted to benefit from the invention is an AKT-5500 plasma
enhanced chemical vapor deposition (PECVD) system, available from
AKT, a division of Applied Materials, Inc., located in Santa Clara,
Calif.
[0021] Each processing chamber 104 is adapted for processing a
large area substrate and typically has a volume of at least about
360 liters. Each processing chamber 104 is typically coupled to a
respective gas delivery system 114. The gas delivery system 114
generally provides process gas to the processing chamber. Each gas
delivery system 114 may be configured to provide one or more gases
to its respective processing chamber 104. In the embodiment
depicted in FIG. 1, at least one of the gas delivery systems 114 is
adapted to provide a process or precursor gas generated from a
liquid precursor at a rate greater than about 1160 sccm (for
example, 10 to at least about 100 grams per minute of TEOS).
[0022] FIG. 2 depicts a sectional view of the processing chamber
104 of FIG. 1 having one embodiment of the gas delivery system 114
coupled thereto. The processing chamber 104 has walls 206, a bottom
208, and a lid assembly 210 that define a process volume 212. The
process volume 212 is typically accessed through a port (not shown)
in the walls 206 that facilitates movement of a substrate 140 into
and out of the processing chamber 104. The walls 206 and bottom 208
are typically fabricated from a unitary block of aluminum or other
material compatible with processing chemistries. The lid assembly
210 contains a pumping plenum 214 that couples the process volume
212 to an exhaust port (that includes various pumping components,
not shown).
[0023] The lid assembly 210 is supported by the walls 206 and can
be removed to service the processing chamber 104. The lid assembly
210 is generally comprised of aluminum and may additionally contain
heat transfer fluid channels for regulating the temperature of the
lid assembly 210 by flowing heat transfer fluid therethrough.
[0024] A distribution plate 218 is coupled to an interior side 220
of the lid assembly 210. The distribution plate 218 is typically
fabricated from aluminum and includes a perforated area through
which process and other gases supplied from the gas delivery system
114 are delivered to the substrate 140 seated on the substrate
support 238. The perforated area of the distribution plate 218 is
configured to distribute process gas in a manner that promotes
uniform deposition of material on the substrate 140.
[0025] A heated substrate support assembly 238 is centrally
disposed within the processing chamber 104. The support assembly
238 supports the substrate 140 during processing. The support
assembly 238 has a plurality of lift pins 250 movably disposed
therethrough. The lift pins 250 may be actuated to project from the
support surface 260, thereby placing the substrate in a
spaced-apart relation to the support assembly 238 to facilitate
substrate transfer with the transfer robot 112.
[0026] A vacuum port (not shown) is disposed through the support
assembly 238 and is used to apply a vacuum between the substrate
140 and the support assembly 238, securing the substrate 140 to the
support assembly 238 during processing. The heating element 232,
such as an electrode disposed in the support assembly 238, is
coupled to a power source 230, heating the support assembly 238 and
the substrate 140 positioned thereon to a predetermined
temperature. Typically, the heating element 232 maintains the
substrate 140 at a uniform temperature of about 150 to at least
about 460 degrees Celsius.
[0027] The support assembly 238 additionally supports a
circumscribing shadow frame 248. The shadow frame 248 is configured
to cover the edge of the substrate 140 and is typically comprised
of ceramic. Generally, the shadow frame 248 prevents deposition at
the edge of the substrate 140 and support assembly 238 so that the
substrate does not stick to the support assembly 238. Optionally, a
purge gas is supplied between the shadow frame 248 and the support
assembly 238 to assist in preventing deposition at the substrate's
edge.
[0028] The support assembly 238 is coupled by a stem 242 to a lift
system (not shown) that moves the support assembly 238 between an
elevated position (as shown) and a lowered position. A bellows 246
provides a vacuum seal between the chamber volume 212 and the
atmosphere outside the processing chamber 104 while facilitating
the movement of the support assembly 238. The stem 242 additionally
provides a conduit for electrical leads, vacuum and gas supply
lines between the support assembly 238 and other components of the
system 100.
[0029] The support assembly 238 generally is grounded such that RF
power supplied by a power source 222 to the distribution plate 218
(or other electrode positioned within or near the lid assembly of
the chamber) may excite the gases disposed in the process volume
212 between the support assembly 238 and the distribution plate
218. The RF power, generally having a frequency of between a few Hz
to 13 MHz or higher is provided in a wattage suitable for the
substrate surface area. In one embodiment, the power source 222
comprises a dual frequency source that provides a low frequency
power at less than about 2 MHz (preferably about 200 to 500 kHz)
and a high frequency power at greater than 13 MHz (preferably about
13.56 MHz). The frequencies may be fixed or variable.
Illustratively, for a 550 mm.times.650 mm substrate, the low
frequency power is about 0.3 to about 2 kW while the high frequency
power is about 1 to about 5 kW. Generally, the power requirements
decrease or increase with a corresponding decrease or increase in
substrate size.
[0030] The gas delivery system 114 includes a tetraethoxysilane
(TEOS) source 272, a helium source 274, and a vaporizer module 280
coupled to the processing chamber 104 by a vaporizer output line
288. The TEOS source 272 includes piping, valves, flow controllers,
and the like, for delivering a controlled quantity of liquid TEOS
to the vaporizer module 280 through a vaporizer input line 276
which runs between the TEOS source 272 and the vaporizer module
280.
[0031] The helium source 274 includes piping, valves, flow
controllers, and the like, for delivering a controlled quantity of
helium gas. The helium can be used in the process as a purge gas by
routing the helium from the helium source 274 through the vaporizer
input line 276 to the vaporizer module 280. The helium can also be
used as a carrier gas to carry the vaporized TEOS into the
processing chamber 104 by routing the helium from the helium source
274 through a carrier gas line 278 that connects with the vaporizer
output line 288.
[0032] FIG. 3A depicts a schematic view of the vaporizer module
280. The vaporizer module is a container 320 that contains a liquid
flow controller 340 and a vaporizer 330. The container 320 also
contains an insulative divider 322 that thermally separates the
flow controller 340 from the vaporizer 330. A conduit 326 runs
through a passage 324 formed in the insulative divider 322 and
couples the flow controller 340 to the vaporizer 330. The container
320 and the insulative divider 322 may be made of any suitable
materials. In the embodiment shown, the container 320 is fabricated
from stainless steel and the insulative divider 322 is fabricated
from silicon rubber.
[0033] The flow controller 340 is coupled to the TEOS source 272 by
vaporizer input line 276 and is coupled to the vaporizer 330 by the
conduit 326. A heat sink 342 is mounted to the bottom of the flow
controller 340. A fan 346 is disposed proximate the heat sink 342
and is oriented such that it blows air across the heat sink 342,
thus maintaining the flow controller at approximately room
temperature, or about 25 degrees Celsius. The flow controller 340
may be any device that controls the flow of a liquid, such as a
mass or volumetric flow meter. One suitable flow controller 340 is
a mass flow meter, model 2000PI, commercially available from Porter
Instrument Company, located in Hatfield, Pa. By thermally isolating
the flow controller 340 from the vaporizer 330, the temperature of
the flow controller 340 may be more readily maintained at a
predefined value for which flow readings provided by the controller
340 are within a known accurately and deviation, thus allowing more
precise control over precursor generation.
[0034] The vaporizer 330 is coupled to the processing chamber 104
by the vaporizer output line 288 and to the flow controller 342 by
the conduit 326. At least one heater 312 is coupled to the
vaporizer module 280 and heats the TEOS in order to facilitate the
vaporization of liquid TEOS into a gas phase. Although shown
coupled to the vaporizer 330, the heater 312 may alternatively be
disposed in or coupled to the conduit 326 or disposed in the
vaporizer 330.
[0035] FIG. 3B depicts an exploded view of one embodiment of the
vaporizer 330. In one embodiment, the vaporizer 330 comprises a
thermally conductive body 352 sealed with a thermally conductive
cap 354. The body 352 has a plurality of transverse channels 360
and a plurality of longitudinal grooves 362 formed in one side. The
body 352 is fabricated from a material inert to the processing
chemistries and of sufficient thickness to retain its flatness
during the fabrication of the plurality channels 360 and the
plurality of grooves 362 and operation of the of the vaporizer 330
at temperatures of about 90 degrees Celsius and higher. It has been
found that the body 352 may be fabricated from stainless steel
having a thickness of at least about 0.125 inches. A stainless
steel body thickness of about 0.100 inches or less has been found
have poor TEOS vaporization performance, generally unsuitable for
low defect deposition due to high liquid content in the output, as
the body 352 is too flexible and/or easily warped during groove
formation such that the gap between the body 352 and the cap 354
varies across the body 352 thereby allowing liquid/gas to flow
outside of the grooves 362 preventing substantially complete
vaporization.
[0036] The transverse channels 360 are disposed perpendicularly to
the direction of flow through the vaporizer 330. One of the
channels 360 is disposed near an inlet side 370 of the vaporizer
330 and is coupled to the conduit 326 via an inlet port 356 formed
at least partially through the body 352. A second one of the
channels 360 is disposed near an outlet side 372 of the vaporizer
330 and is coupled to the vaporizer output line 288 via an outlet
port 358 (shown partially obscured in FIG. 3B) formed at least
partially through the body 352.
[0037] The plurality longitudinal grooves 362 are formed in the
body 352 and run parallel to the direction of flow through the
vaporizer 330 and fluidly couple the plurality of channels 360 to
each other. The grooves 362 are shallower than the channels 360 and
are machined in order to maintain the flatness required to maintain
separate flow streams of TEOS through adjacent grooves 362 to
ensure complete vaporization. It has been found that the heat
generated by chemical etching of the grooves 362 warps the body
352, thereby preventing stream isolation within the grooves 362
that substantially prevents complete vaporization of TEOS. Mixing
of the flow streams will result in poor performance and excessive
droplet generation, which is unacceptable for large area substrate
processing. The cap 354 is fastened to the body 352, thereby
forcing the fluid flowing through the vaporizer 330 to travel only
within the plurality of channels 360 and the plurality of grooves
362 formed therein.
[0038] The grooves 362 are configured with sufficient surface area
to ensure substantially complete vaporization of at least about 10
to at least about 100 grams per minute of TEOS. In one embodiment,
at least 45 grooves 362 are formed in the body 352. Each groove 362
has a depth of about 0.007 inches and a width of about 0.015
inches.
[0039] The body 352 and cap 354 are heated by at least one heater
312 disposed against the body 352 and/or the cap 354 to heat the
TEOS flowing through the channels 360 and grooves 362 to between
about 90 to about 150 degrees Celsius, preferably 120 degrees
Celsius. Liquid TEOS entering the vaporizer 330 is thus heated and
forced to traverse the longitudinal grooves 362, producing TEOS
vapor.
[0040] As the TEOS substantially vaporizes completely, the vacuum
pump-down time has been substantially reduced. For example, large
area substrate CVD systems utilizing vaporizer 330 have pump-down
times of about 15 seconds when producing 5 g/min TEOS and about 18
seconds for conventional vaporizers producing 10 g/min TEOS as
respectively compared to pump down times of 21 and 34 seconds for
conventional vaporizers. Thus, the vaporizer 330 demonstrates a
substantial reduction in the percent of liquid entering the
processing chamber, thus enabling reduced cycle times and desirably
increased substrate throughput as compared to conventional systems
discussed above.
[0041] Additionally, the stabilization time and pressure stability
of the vaporizer output is substantially improved over conventional
vaporizers. For example, the inventive vaporizer has a
stabilization time (i.e., time to steady state output) of about 10
seconds as compared to 20-45 second in conventional vaporizers when
producing 10 grams per minute TEOS. The pressure stability of the
inventive vaporizer is about .+-.2.82 percent as compared to
.+-.6.09 percent in conventional vaporizers when producing 10 grams
per minute TEOS.
[0042] Returning to additionally to FIG. 2, a restrictor 290 is
disposed in the vaporizer output line 288 between the vaporizer 330
and the processing chamber 104. The restrictor 290 is configured to
provide sufficient backpressure to the vaporizer 330 to that the
vaporizing liquid does not expand so rapidly as to exit the
vaporizer 330 before complete vaporization. Moreover, the
restrictor 290 provides a stabilized flow of vaporized TEOS that
enhances uniform and repeatable processing. In one embodiment, the
restrictor 290 has an orifice of between about 0.187 and about
0.140 inches.
[0043] In order to prevent condensation of the vaporized TEOS
before reaching the chamber 104, the vaporizer output line 288 and
carrier gas line 278 are heated. This prevents cooling of the
vaporized TEOS upon traveling through the vaporizer output line 288
or upon mixing with a colder, non-heated carrier gas. The lines
278, 288 may be heated by wrapping with heater tape, applying
contact heaters, routing through heat transfer conduits, and the
like. The vaporized TEOS or TEOS/carrier gas mixture flows through
vaporizer output line 288 to the processing chamber 104. This
combination of vaporizer module 280 and heated lines 288, 278 will
allow vaporized TEOS to be delivered to the processing chamber 104
at a rate in excess of 10 grams per min. In other embodiments,
vaporizer module 280 may be configured to deliver at least about 20
grams per minute, and up to and exceeding 100 grams per minute. One
attribute of the vaporizer module 280 that facilitates higher
capacity vaporizers is to increase the number of grooves 362 formed
in the vaporizer module 280.
[0044] Oxygen gas is provided into the processing chamber from an
oxygen source 284 that is coupled to the processing chamber by a
plasma gas line 286. The oxygen gas mixes with the TEOS vapor and
is excited in the processing chamber 104 to form a plasma. The TEOS
decomposes in the plasma and deposits a layer of silicon oxide on
the surface of a substrate located in the processing chamber
104.
[0045] Typically, a remote plasma source (not shown) is coupled to
the processing chamber 104 and used to clean the chamber after a
number of process cycles have been completed. The processing
chamber may be cleaned after every cycle or after a predetermined
number of cycles in order to maintain the required level of
cleanliness within the chamber while minimizing costly downtime and
product defects due to contamination.
[0046] FIG. 4 depicts a flow diagram for a method 400 for plasma
enhanced chemical vapor deposition of a dielectric material on
large area substrates. At step 402, referring to FIGS. 2-3, the
substrate 140 is introduced into the processing chamber 104 and is
placed on the substrate support assembly 238 within the processing
chamber 104. The substrate 140 is held down by vacuum pressure and
is covered around its periphery by the shadow frame 248.
[0047] At step 404, the substrate 140 is heated by heating element
232 to a temperature within the range of about 350 to about 440
degrees Celsius. Typically, the walls 206 of the processing chamber
104 are cooled to maintain the processing chamber 104 at a
temperature in the range of from about 90 to about 150 degrees
Celsius.
[0048] The process gases are introduced into the processing chamber
104 at step 406. In one embodiment, TEOS is supplied from the TEOS
source 272 to the vaporizer 276 at a flow rate of from about 1,160
to about 11,600 sccm. The vaporizer 276 and the vaporizer output
pipe 284 are maintained at a temperature of from about 90 to about
150 degrees Celsius, preferably 120 degrees Celsius. The TEOS
flowing through the heated vaporizer is vaporized and the TEOS
vapor flows out the vaporizer output pipe 284 into the processing
chamber 104.
[0049] The TEOS vapor flowing through the vaporizer output pipe 284
enters the processing chamber 104 through the lid assembly 210.
Oxygen gas flowing from the oxygen gas source 284 through the
plasma gas line 286 is simultaneously introduced into the
processing chamber 104 through the lid assembly 210. The oxygen gas
flow rate is about 2,000 to about 15,000 sccm. The TEOS and oxygen
gases mix and move into the process volume 212 through the gas
distribution plate 218.
[0050] At step 408, a plasma is formed within the processing
chamber 104 in the process volume 212 from the mixed TEOS and
oxygen by applying about 5,000 W of RF energy from the power source
222 to the gas distribution plate 218. The TEOS decomposes in the
plasma and deposits a layer of silicon oxide on the surface of the
substrate at a rate of about 3000 to at least about 3500 Angstroms
per minute on the exposed surface of a large area substrate having
a one side surface area of at least about 0.357 m.sup.2 when
flowing TEOS at a rate of about 1,160 sccm. Deposition rates of
about 14,000 .ANG./M may be realized at TEOS flow rates of 11,600
sccm.
[0051] In one embodiment, the substrate 140 is heated by heating
element 232 to a temperature of about 440 degrees Celsius. TEOS is
supplied from the TEOS source 272 to the vaporizer 276 at a flow
rate of about at least about 10 grams per minute. The vaporizer is
maintained at a temperature of about 120 degrees Celsius. The TEOS
flowing through the heated vaporizer is vaporized and flows out the
vaporizer output pipe 284 into the processing chamber 104. The
vaporizer output pipe 284 is heated to a temperature of about 120
degrees Celsius to prevent condensation of TEOS vapor before entry
into the processing chamber 104.
[0052] The TEOS vapor flowing through the vaporizer output pipe 284
enters the processing chamber 104 through the lid assembly 210.
Oxygen gas flowing from the oxygen gas source 284 through the
plasma gas line 286 is simultaneously introduced into the
processing chamber 104 through the lid assembly 210 at a flow rate
of about 2,000 sccm. The TEOS and Oxygen gases mix and move into
the process volume 212 through the gas distribution plate 218. A
plasma is formed in the process volume 212 from the mixed gases by
applying about 5,000 W of RF energy from the power source 222 to
the gas distribution plate 218 and a layer of silicon oxide is
deposited on the surface of the substrate at a rate of about 3000
to at least about 4,000 Angstroms per minute.
[0053] The silicon oxide material deposited through the method 400
is not only deposited at a rate substantially greater than
conventional processes, but the silicon oxide layer also exhibits
robust physical properties. For example, the deposited silicon
oxide has a stress in the range of -2.68 to 3.03; a refractive
index of from about 1.45 to about 1.47; and a wet etch rate of from
about 1,250 to about 3,100 Angstroms per minute, all of which
compare favorably with conventionally applied materials deposited
at much slower rates.
[0054] While the foregoing is directed to the preferred embodiment
of the present invention, other and further embodiments of the
invention may be devised without departing from the basic scope
thereof. The scope of the invention is determined by the claims
that follow.
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