U.S. patent application number 11/564167 was filed with the patent office on 2008-05-29 for gas baffle and distributor for semiconductor processing chamber.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Farhan Ahmad, Sanjay Kamath, Young S. Lee, Siqing Lu, Hemant P. Mungekar, Soonam Park.
Application Number | 20080124944 11/564167 |
Document ID | / |
Family ID | 39494939 |
Filed Date | 2008-05-29 |
United States Patent
Application |
20080124944 |
Kind Code |
A1 |
Park; Soonam ; et
al. |
May 29, 2008 |
GAS BAFFLE AND DISTRIBUTOR FOR SEMICONDUCTOR PROCESSING CHAMBER
Abstract
Apparatus and methods for distributing gas in a semiconductor
process chamber are provided. In an embodiment, a gas distributor
for use in a gas processing chamber comprises a body. The body
includes a baffle with a gas deflection surface to divert the flow
of a gas from a first direction to a second direction. The gas
deflection surface comprises a concave surface. The concave surface
comprises at least about 75% of the surface area of the gas
deflection surface. The concave surface substantially deflects the
gas toward a chamber wall and provides decreased metal atom
contamination from the baffle so that season times can be
reduced.
Inventors: |
Park; Soonam; (Sunnyvale,
CA) ; Ahmad; Farhan; (Sunnyvale, CA) ;
Mungekar; Hemant P.; (San Jose, CA) ; Kamath;
Sanjay; (Fremont, CA) ; Lee; Young S.; (San
Jose, CA) ; Lu; Siqing; (San Jose, CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW LLP / AMAT
TWO EMBARCADERO CENTER, EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
Applied Materials, Inc.
Santa Clara
CA
|
Family ID: |
39494939 |
Appl. No.: |
11/564167 |
Filed: |
November 28, 2006 |
Current U.S.
Class: |
438/778 |
Current CPC
Class: |
C23C 16/4404 20130101;
C23C 16/45563 20130101; C23C 16/4401 20130101 |
Class at
Publication: |
438/778 |
International
Class: |
H01L 21/31 20060101
H01L021/31; H01L 21/469 20060101 H01L021/469 |
Claims
1. A method of processing a semiconductor wafer in a semiconductor
process chamber, the method comprising: cleaning the chamber with a
clean gas. seasoning the chamber for about 25 to 60 seconds;
placing the wafer in the chamber to coat the wafer with a
dielectric layer; coating the wafer with the dielectric layer with
an HDP-CVD process, the layer having no more than about
2.times.10.sup.12 metal atoms per square centimeter; and removing
the coated wafer from the chamber.
2. The method of claim 1 wherein the HDP-CVD process comprises at
least one of a medium power HDP-CVD process or a high power HDP-CVD
process.
3. The method of claim 1 wherein the chamber is seasoned for about
25 to 45 seconds.
4. The method of claim 1 wherein the chamber is seasoned for about
25 to 35 seconds.
5. The method of claim 1 wherein the dielectric layer has from
about 0.3.times.10.sup.12 to 2.0.times.10.sup.12 metal atoms per
square centimeter.
6. The method of claim 1 wherein the dielectric layer has from
about 0.3.times.10.sup.12 to 1.5.times.10.sup.12 metal atoms per
square centimeter.
7. The method of claim 1 wherein the dielectric layer has from
about 0.3.times.10.sup.12 to 1.0.times.10.sup.12 metal atoms per
square centimeter.
8. The method of claim 1 wherein the metal is aluminum.
9. The method of claim 1 further comprising deflecting the clean
gas toward the chamber wall with a concave gas deflection
surface.
10. The method of claim 1 wherein the total time to clean the
chamber, season the chamber, place the wafer in the chamber,
process the wafer in the chamber and remove the wafer from the
chamber corresponds to a throughput of at least about 8 wafers per
hour.
11. The method of claim 1 further comprising deflecting the clean
gas with a baffle, wherein the metal atoms of the dielectric layer
comprises a dominant metal element and the dominant metal element
corresponds to a dominant metal element of the baffle.
12. A semiconductor substrate processing device, the device
comprising: an enclosure having a ceiling and a sidewall; a
substrate support adapted to support a semiconductor substrate with
the enclosure; a high density plasma deposition system adapted to
deliver a high density plasma to the semiconductor substrate to
form a dielectric layer on the substrate; a gas distributor
positioned centrally above the substrate support to deliver a
deposition gas to a substrate, the gas distributor comprising a
baffle to deflect a gas toward the sidewall; a gas delivery system
adapted to control gas delivery to the gas distributor; a processor
coupled to the gas delivery system and the plasma deposition system
to season the chamber and a apply the dielectric layer to the
wafer; and wherein the baffle and the enclosure are adapted to
provide no more than about 1.5.times.10.sup.12 metal atoms per
square centimeter on the layer for a high power process with a
season time of about 25 to 60 seconds.
13. The device of claim 12 wherein the plasma deposition system is
adapted to provide the dielectric layer with a thickness from about
4000 A to 8000 A.
14. The device of claim 12 wherein the plasma deposition system is
adapted to deliver a medium power process, and the baffle and the
enclosure are adapted to provide no more than about
1.0.times.10.sup.12 metal atoms per square centimeter on the
dielectric layer for a medium power process with a season time of
about 25 to 60 seconds.
15. The device of claim 12 wherein the enclosure and the gas
distributor are adapted so that the metal atoms of the dielectric
layer comprises a dominant metal element and the dominant metal
element corresponds to a dominant metal element of the baffle.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to the field of
semiconductor manufacturing. More particularly the present
invention relates to a gas baffles and processes for delivering
gases used in the formation of integrated circuits.
[0002] One of the primary steps in the fabrication of modern
semiconductor devices is the formation of a film, such as a silicon
oxide film, on a semiconductor substrate. Silicon oxide is widely
used as a dielectric layer in the manufacture of semiconductor
devices. As is well known, a silicon oxide film can be deposited by
a thermal chemical-vapor deposition ("CVD") process or by a
plasma-enhanced chemical-vapor deposition ("PECVD") process. In a
conventional thermal CVD process, reactive gases are supplied to a
surface of the substrate, where heat-induced chemical reactions
take place to produce a desired film. In a conventional
plasma-deposition process, a controlled plasma is formed to
decompose and/or energize reactive species to produce the desired
film.
[0003] Semiconductor device geometries have decreased significantly
in size since such devices were first introduced several decades
ago, and continue to be reduced in size. This continuing reduction
in the scale of device geometry has resulted in a dramatic increase
in the density of circuit elements and interconnections formed in
integrated circuits fabricated on a semiconductor substrate. One
persistent challenge faced by semiconductor manufacturers in the
design and fabrication of such densely packed integrated circuits
is the desire to prevent spurious interactions between circuit
elements, a goal that has required ongoing innovation as geometry
scales continue to decrease.
[0004] Unwanted interactions are typically prevented by providing
spaces between adjacent elements that are filled with a dielectric
material to isolate the elements both physically and electrically.
Such spaces arc sometimes referred to herein as "gaps" or
"trenches," and the processes for filling such spaces are commonly
referred to in the art as "gap-fill" processes. The ability of a
given process to produce a film that completely fills such gaps is
thus often referred to as the "gap-fill ability" of the process,
with the film described as a "gap-fill layer" or "gap-fill film."
As circuit densities increase with smaller feature sizes, the
widths of these gaps decrease, resulting in an increase in their
aspect ratio, which is defined by the ratio of the gap's height to
its depth. High-aspect-ratio gaps are difficult to fill completely
using conventional CVD techniques, which tend to have relatively
poor gap-fill abilities. One family of dielectric films that is
commonly used to fill gaps in intermetal dielectric ("IMD")
applications, premetal dielectric ("PMD") applications, and
shallow-trench-isolation ("STI") applications, among others, is
silicon oxide (sometimes also referred to as "silica glass" or
"silicate glass").
[0005] Some integrated circuit manufacturers have turned to the use
of high-density plasma CVD ("HDP-CVD") systems in depositing
silicon oxide gap-fill layers. Such systems form a plasma that has
a density greater than about 10.sup.11 ions/cm.sup.3, which is
about two orders of magnitude greater than the plasma density
provided by a standard capacitively coupled plasma CVD system.
Inductively coupled plasma ("ICP") systems are examples of HDP-CVD
systems. One factor that allows films deposited by such HDP-CVD
techniques to have improved gap-fill characteristics is the
occurrence of sputtering simultaneous with deposition of material.
Sputtering is a mechanical process by which material is ejected by
impact, and is promoted by the high ionic density of the plasma in
HDP-CVD processes. The sputtering component of HDP deposition thus
slows deposition on certain features, such as the corners of raised
surfaces, thereby contributing to the increased gap-fill
ability.
[0006] Even with the use of HDP and ICP processes, there remain a
number of persistent challenges in achieving desired deposition
properties. These include the need to manage thermal
characteristics of the plasma within a processing chamber,
particularly with high-energy processes that may result in
temperatures that damage structures in the chamber and cause
contamination. For example, high temperatures have been associated
with the formation and sublimation of AlF.sub.3, resulting in
erosion system components exposed to such high temperatures and
deposition of the aluminum impurities on substrates. Fluorine is
highly corrosive and often present in chambers a clean gas to
corrosively remove material from the chamber wall and also as an
etch gas. For example, dissociated NF.sub.3 can be introduced into
the chamber from a back-side of the baffle to clean the chamber or
as an etch component of deposition-etch-deposition recipes which
use NF.sub.3 plasma within the chamber.
[0007] In addition, there is a general desire to provide deposition
processes that are uniform across a wafer. Non-uniformities lead to
inconsistencies in device performance and may result from a number
of different factors. The deposition characteristics at different
points over a wafer result from a complex interplay of a number of
different effects. For example, the way in which gas is introduced
into the chamber, the level of power used to ionize precursor
species, the use of electrical fields to direct ions, and the like,
may ultimately affect the uniformity of deposition characteristics
across a wafer. In addition, the way in which these effects are
manifested may depend on the physical shape and size of the
chamber, such as by providing different diffusive effects that
affect the distribution of ions in the chamber.
[0008] Work in relation with embodiments of the present invention
suggests the current systems and methods may be less than ideal.
For example, as semiconductor circuits and the associated gaps
between circuit elements shrink, contamination by small particles
can become problematic, especially where the particle size
approximates the size of a gap. Also, contamination with metal in
the gap-fill layer, for example Al, can decrease the desired
electrically insulative properties of the dielectric gap-fill
layer. This contamination can result in decreased yields, wasted
material and in some instances faulty circuits. As a result, one
specification of HDP-CVD process films for shallow trench isolation
is Al content of the film.
[0009] One approach to prevent wafer contamination has been to
season the chamber with a protective coating prior to placing a
wafer in the chamber. For example, process chambers are often
seasoned with a deposition gas, for example SiH.sub.4, that
deposits a protective coating inside the chamber, for example on
the chamber walls, to prevent contamination and protect the chamber
from erosion by the clean gas. However, seasoning the chamber with
a protective coating takes time, and a typical season time can be
on the order of 120 seconds. As a result, the throughput, the
number of wafers processed over a given period of time, is
decreased, and the throughput of current semiconductor process
systems may be less than ideal. Work in relation with the present
invention suggests that wafer production throughput can be
increased by decreasing the amount of time required to process a
wafer, for example by decreasing the season time. Shown in FIG. 1
is an embodiment of a prior art gas baffle that has been used in
semiconductor process chambers and shown to present at least some
of the shortcomings described above.
[0010] There is accordingly a general need in the art for improved
systems and methods providing deposition uniformity with decreased
contamination from metal atoms, for example aluminum atoms, and
increased throughput in HDP and ICP processes.
BRIEF SUMMARY OF THE INVENTION
[0011] Embodiments of the present invention provide methods and an
apparatus for processing semiconductors. More particularly,
embodiments of the present invention provide a gas distributor used
to distribute a gas in a processing chamber, for example a clean
gas and/or a deposition gas.
[0012] In one embodiment of the present invention, gas distributor
for use in a semiconductor processing chamber comprises a body. The
body includes a baffle with a gas deflection surface to divert the
flow of a gas from a first direction to a second direction. The gas
deflection surface comprises a concave portion. The concave portion
comprises at least about 75% of the surface area of the gas
deflection surface.
[0013] In another embodiment of the present invention, a substrate
processing chamber comprises an enclosure having a ceiling and a
sidewall, and a substrate support adapted to support a substrate. A
gas distributor is positioned centrally above the substrate
support. The gas distributor comprises a body that includes a
baffle. The baffle has an upper exposed surface adapted to
outwardly direct gas away from the body and towards the enclosure
sidewall. The upper exposed surface comprises a concave portion,
and the concave portion comprises at least about 75% of the area of
the upper exposed surface of the baffle. The distributor comprises
a lower surface below the upper surface and spaced apart from the
substrate support. The lower surface is adapted to inject a
deposition gas into the chamber.
[0014] In an additional embodiment of the present invention, a gas
distributor for use in a gas processing chamber comprises a body.
The body includes a baffle to divert a gas. The baffle comprises a
concave surface to deflect the gas from a first direction to a
second direction. The baffle also includes a convex surface
disposed peripheral to the concave surface. A transition surface is
disposed between the concave surface and the convex surface to
provide a transition from the concave surface to the convex
surface. The convex surface comprises a maximum with across the
baffle. The transition surface extends along the for no more than
about 20% of the maximum width.
[0015] In a further embodiment of the present invention, a method
of deflecting a gas used in a semiconductor process is provided. A
clean gas is directed toward a gas distributor in a first
direction. The gas distributor comprises a concave surface. The gas
is deflected from the first direction to a second direction
substantially with the concave surface. The second direction is
transverse to the first direction.
[0016] In another embodiment of the present invention, a method of
processing a semiconductor wafer in a semiconductor process chamber
is provided. The method comprises cleaning the chamber with a clean
gas. The chamber is seasoned for about 25 to 60 seconds. The wafer
is placed in the chamber to coat the wafer with a dielectric layer.
The wafer is coated with the dielectric layer with an HDP process
and/or a CVD process. The dielectric layer has no more than about
2.times.10.sup.12 metal atoms per square centimeter. The coated
wafer is removed from the chamber.
[0017] In yet another embodiment of the present invention, a
substrate processing device is provided. The device includes an
enclosure having a ceiling and a sidewall. A substrate support is
adapted to support a semiconductor substrate within the enclosure.
A high density plasma deposition system is adapted to deliver a
high density plasma to the substrate to form a dielectric layer on
the substrate. A gas distributor is positioned centrally above the
substrate support. A gas delivery system is adapted to control gas
delivery to the gas distributor. A processor is coupled to the gas
delivery system and the plasma deposition system to season the
chamber and apply the dielectric layer to the wafer. The baffle and
the enclosure are adapted to provide no more than about
1.5.times.10.sup.12 metal atoms per square centimeter on the layer
for a high power process with a season time of about 25 to 60
seconds.
[0018] Many benefits are achieved by the present invention over
conventional techniques. Embodiments of the present invention use a
concave surface to deflect the gas and direct the gas toward the
chamber wall to provide decreased wafer contamination, for example
decreased aluminum contamination. Also, embodiments of the present
invention provide decreased metal atom contamination, for example
aluminum atom contamination, of the gap-fill layer with reduced
season times, so that the total amount of time required to process
a semiconductor wafer is reduced. At least some of these benefits
are provided by the embodiments of the present invention described
herein below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a cross-sectional view of a previously known gas
distributor;
[0020] FIG. 2 is a simplified cross-sectional view of an exemplary
ICP reactor system;
[0021] FIG. 3A is a cross-sectional view of a gas distributor
according to an embodiment of the present invention;
[0022] FIG. 3B is a cross-sectional view of a gas distributor
positioned in a semiconductor processing chamber according to an
embodiment of the present invention;
[0023] FIG. 3C is a top view of a gas distributor as in FIG. 3A
according to the embodiment of the present invention;
[0024] FIG. 4 is a cross-sectional view of a gas distributor with a
truncated gas deflection surface according to an embodiment of the
present invention; and
[0025] FIG. 5 is a cross-sectional view of a gas distributor with
an annular flat portion extending between concave and convex gas
deflection surfaces according to an embodiment of the present
invention;
[0026] FIG. 6 is a flow chart illustrating a method of processing a
wafer with a decreased season time and decreased Al contamination,
in accordance with an embodiment of the present invention;
[0027] FIG. 7 shows a comparison of clean end-points comparison for
a gas distributor as in FIG. 1 versus a gas distributor as in FIG.
3 according to an embodiment of the present invention; and
[0028] FIG. 8 shows a comparison of Al contamination in a
processing chamber with a previously known gas distributor as in
FIG. 1 versus a gas distributor as in FIG. 3 according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0029] Embodiments of the present invention provide methods and an
apparatus for processing semiconductors. More particularly,
embodiments of the present invention provide a gas distributor used
to distribute clean gas and to distribute a deposition gas in a
processing chamber.
[0030] FIG. 1 shows a previously known gas distributor. Gas
distributor 100 has a gas deflecting surface 102 and a gas
distributor face 104. Gas deflecting surface 102 provides a pathway
for cleaning gases during a chamber clean process. Cleaning gases
are directed to the chamber walls instead of a substrate support
member located directly below the gas distributor. The gas
distributor 100 is connected to a chamber wall at a proximal
portion 106. During a CVD process, a deposition gas is supplied to
the gas distributor 100 at the proximal end 108. This deposition
gas flows through gas distributor 100, exiting at apertures 110,
and onto a substrate position on the substrate support member. As
illustrated in FIG. 1, apertures 110 are disposed on the gas
distributor face 104 at a step 112, a raised surface.
[0031] 1. Exemplary ICP Chamber
[0032] The inventors have implemented embodiments of the invention
with the ULTIMA.TM. system manufactured by APPLIED MATERIALS, INC.,
of Santa Clara, Calif., a general description of which is provided
in commonly assigned U.S. Pat. Nos. 5,994,662; 6,170,428; and
6,450,117; and U.S. patent application Ser. Nos. 10/963030 and
11/075527; the entire disclosures of these patents and applications
are incorporated herein by reference. An overview of the ICP
reactor is provided in connection with FIG. 2. FIG. 2 schematically
illustrates the structure of an exemplary HDP-CVD system 210 in one
embodiment. The system 210 includes a chamber 213, a vacuum system
270, a source plasma system 280A, a bias plasma system 280B, a gas
delivery system 233, and a remote plasma cleaning system 250.
Although remote plasma cleaning system 250 is shown on the lower
part of the system, other locations are possible, for example near
the top of the chamber as described in U.S. application Ser. No.
10/963030, the full disclosure of which has been previously
incorporated herein by reference.
[0033] The Upper portion of chamber 213 includes a dome 214, which
is made of a ceramic dielectric material, such as aluminum oxide or
aluminum nitride, sapphire, SiC or quartz. A heater plate 223 and a
cold plate 224 surmount, and are thermally coupled to, dome 214.
Heater plate 223 and cold plate 224 allow control of the dome
temperature to within about .+-.10.degree. C. over a range of about
100.degree. C. to 200.degree. C. Dome 214 defines an upper boundary
of a plasma processing region 216. Plasma processing region 216 is
bounded on the bottom by the upper surface of a substrate 217 and a
substrate support member 218.
[0034] The lower portion of chamber 213 includes a body member 222,
which joins the chamber to the vacuum system. A base portion 221 of
substrate support member 218 is mounted on, and forms a continuous
inner surface with, body member 222. Substrates are transferred
into and out of chamber 213 by a robot blade (not shown) through an
insertion/removal opening (not shown) in the side of chamber 213.
Lift pins (not shown) are raised and then lowered under the control
of a motor (also not shown) to move the substrate from the robot
blade at an upper loading position 257 to a lower processing
position 256 in which the substrate is placed on a substrate
receiving portion 219 of substrate support member 218. Substrate
receiving portion 219 includes an electrostatic chuck 220 that
secures the substrate to substrate support member 218 during
substrate processing. In a preferred embodiment, substrate support
member 218 is made from an aluminum oxide or aluminum ceramic
material.
[0035] Vacuum system 270 includes throttle body 225, which houses
twin-blade throttle valve 226 and is attached to gate valve 227 and
turbo-molecular pump 228. It should be noted that throttle body 225
offers minimum obstruction to gas flow, and allows symmetric
pumping. Gate valve 227 can isolate pump 228 from throttle body
225, and can also control chamber pressure by restricting the
exhaust flow capacity when throttle valve 226 is fully open. The
arrangement of the throttle valve, gate valve, and turbo-molecular
pump allow accurate and stable control of chamber pressures from
between about 1 millitorr to about 2 torr.
[0036] A gas delivery system 233 provides gases from several
sources, 234A-234E chamber for processing the substrate via gas
delivery lines 238 (only some of which are shown). As would be
understood by a person of skill in the art, the actual sources used
for sources 234A-234E and the actual connection of delivery lines
238 to chamber 213 varies depending on the deposition and cleaning
processes executed within chamber 213. Gases are introduced into
chamber 213 through a gas ring 237 and/or a gas distributor
211.
[0037] In one embodiment, first and second gas sources, 234A and
234B, and first and second gas flow controllers, 235A' and 235B',
provide gas to ring plenum in gas ring 237 via gas delivery lines
238 (only some of which are shown). Gas ring 237 has a plurality of
source gas nozzles 239 (only one of which is shown for purposes of
illustration) that provide a uniform flow of gas over the
substrate. Nozzle length and nozzle angle may be changed to allow
tailoring of the uniformity profile and gas utilization efficiency
for a particular process within an individual chamber. In a
preferred embodiment, gas ring 237 has 12 source gas nozzles made
from an aluminum oxide ceramic.
[0038] Gas ring 237 also has a plurality of oxidizer gas nozzles
240 (only one of which is shown), which in a preferred embodiment
are co-planar with and shorter than source gas nozzles 239, and in
one embodiment receive gas from body plenum. In some embodiments it
is desirable not to mix source gases and oxidizer gases before
injecting the gases into chamber 213. In other embodiments,
oxidizer gas and source gas may be mixed prior to injecting tile
gases into chamber 213 by providing apertures (not shown) between
body plenum and gas ring plenum. In one embodiment, third, fourth,
and fifth gas sources, 234C, 234D, and 234D', and third and fourth
gas flow controllers, 235C and 235D', provide gas to body plenum
via gas delivery lines 238. Additional valves, such as 243B (other
valves not shown), may shut off gas from the flow controllers to
the chamber.
[0039] In embodiments where flammable, toxic, or corrosive gases
are used, it may be desirable to eliminate gas remaining in the gas
delivery lines after a deposition. This may be accomplished using a
3-way valve, such as valve 243B, to isolate chamber 213 from
delivery line 23 8A and to vent delivery line 238A to vacuum
foreline 244, for example. As shown in FIG. 2, other similar
valves, such as 243A and 243C, may be incorporated on other gas
delivery lines.
[0040] Referring again to FIG. 2, chamber 213 also has gas
distributor 211 and top vent 246. Gas distributor 211 and top vent
246 allow independent control of top and side flows of the gases,
which improves film uniformity and allows fine adjustment of the
film's deposition and doping parameters. Top vent 246 is an annular
opening around gas distributor 211. Gas distributor 211 includes a
plurality of apertures in a step according to an embodiment of the
present invention for improved gas distribution. In one embodiment,
first gas source 234A supplies source gas nozzles 239 and L;as
distributor 211. Source nozzle MFC 235A' controls the amount of gas
delivered to source gas nozzles 239 and top nozzle MFC 235A
controls the amount of gas delivered to gas distributor 211.
Similarly, two MFCs 235B and 235B' may be used to control the flow
of oxygen to both top vent 246 and oxidizer gas nozzles 240 from a
single source of oxygen, such as source 234B. The gases supplied to
gas distributor 211 and top vent 246 may be kept separate prior to
flowing the gases into chamber 213, or the gases may be mixed in
top plenum 248 before they flow into chamber 213. Separate sources
of the same gas may be used to supply various portions of the
chamber.
[0041] System controller 260 controls the operation of system 210.
In a preferred embodiment, controller 260 includes a memory 262,
which comprises a tangible medium such as a hard disk drive, a
floppy disk drive (not shown), and a card rack (not shown) coupled
to a processor 261. The card rack may contain a single-board
computer (SBC) (not shown), analog and digital input/output boards
(not shown), interface boards (not shown), and stepper motor
controller boards (not shown). The system controller conforms to
the Versa Modular European ("VME") standard, which defines board,
card cage, and connector dimensions and types. The VME standard
also defines the bus structure as having a 16-bit data bus and
24-bit address bus. System controller 260 operates under the
control of a computer program stored on the tangible medium for
example the hard disk drive, or through other computer programs,
such as programs stored on a removable disk. The computer program
dictates, for example, the timing, mixture of gases, RF power
levels and other parameters of a particular process. The interface
between a user and the system controller is via a monitor, such as
a cathode ray tube ("CRT"), and a light pen.
[0042] System controller 260 controls the season time of the
chamber and gases used to season the chamber, the clean time and
gases used to clean the chamber, and the application of plasma with
the HDP CVD process. To achieve this control, the system controller
260 is coupled to many of the components of system 210. For
example, system controller 260 is coupled to vacuum system 270,
source plasma system 280A, bias plasma system 280B, gas delivery
system 233, and remote plasma cleaning system 250. System
controller 260 is coupled to vacuum system 270 with a line 263.
System controller 260 is coupled to source plasma system 280 with a
line 264A and to bias plasma system 280B with a line 264B. System
controller 260 is coupled to gas delivery system 233 with a line
265. System controller 260 is coupled to remote plasma cleaning
system 250 with a line 266. Lines 263, 264A, 264B, 265 and 266
transmit control signals from system controller 260 to vacuum
system 270, source plasma system 280A, bias plasma system 280B, gas
delivery system 233, and remote plasma cleaning system 250,
respectively. It will be understood that system controller 260 can
include several distributed processors to control the components of
system 21(0.
[0043] 2. Baffle Characteristics
[0044] Embodiments of the present invention described herein use a
concave surface of a baffle to substantially deflect and
substantially direct a clean gas horizontally toward a chamber wall
in HDP-CVD processes. By deflecting the clean gas with the concave
surface and directing the clean gas toward the chamber wall with
the concave surface, heat is readily conducted from gas deflection
surfaces of the baffle. This heat conduction results from the
baffle shape associated with concave gas deflection surface. The
use of the concave gas deflection surface to substantially deflect
and substantially direct clean gas toward the chamber wall also
permits clean gas deflection and direction without the use of a
substantial extended flange.
[0045] At least two mechanisms are believed to contribute Al wafer
contamination. One mechanism is formation of aluminum fluoride
(AlF.sub.3). A baffle is typically made of a single piece of
aluminum nitride (AlN) or aluminum oxide (Al.sub.2O.sub.3), and
either of these materials can react with fluorine to form aluminum
fluoride. Formation of AlF.sub.3 on the baffle is related to baffle
temperature during the clean/etch steps. Another mechanism that
contributes to wafer contamination is AlF.sub.3 sublimation. As a
result of these two mechanisms, AlF.sub.3 is formed on the baffle
by chemical reaction and is subsequently removed by sublimation,
thereby allowing more AlN or Al.sub.2O.sub.3 to react with
fluorine. Lower temperatures of the baffle during the clean etch
steps results in less sublimation of the AlF.sub.3. As sublimated
AlF.sub.3 is deposited on the semiconductor wafer substrate, less
AlF.sub.3 sublimation results in less Al on the film formed with a
gap-fill process.
[0046] Deflecting and directing the clean gas toward the chamber
wall with the concave surface can result in decreased Al
contamination on the gap fill layer of the processed wafer.
Typically, wafer contamination from metal atoms includes a dominant
species of metal atoms deposited in the wafer. This dominant
species of metal atoms in the wafer corresponds to a dominant
species of metal atoms in the gas distributor, for example Al metal
atoms from an AlN gas distributor. By decreasing sublimation and
chemical reactions on the baffle, the amount of metal atoms removed
from the baffle during the deposition process is decreased and the
number of metal atoms deposited on the wafer is decreased. Thus,
the season time can be reduced because a thinner protective coating
on the baffle will provide low Al contamination. As a result,
semiconductor wafer throughput is increased while still providing
low Al wafer contamination.
[0047] Embodiments of the present invention can be used with low,
medium and high power HDP/CVD processes. High power process
typically include power with a range from about 15 to 18 kW. Medium
power processes typically include power with a range from about 8
to 12 kW. Low power processes are generally under about 8 kW. Many
embodiments of the present invention can be used to process 300 mm
wafers, although other wafer sizes, for example 200 mm wafers and
450 mm wafers can be processed with embodiments of the present
invention.
[0048] FIG. 3A is a cross-sectional view of a gas distributor
according to an embodiment of the present invention. This diagram
is merely an example, which should not unduly limit the scope of
the claims herein. One of ordinary skill in the art would recognize
other variations, modifications, and alternatives. As shown, the
present invention provides a gas distributor 300 for introducing a
gas into a semiconductor processing chamber. Gas distributor 300 is
made of aluminum nitride (AlN), and can be made with any suitable
material such as aluminum oxide (alumina, Al.sub.2O.sub.3), silicon
carbide (SiC), zirconium, quartz, sapphire and the like. In this
embodiment, gas distributor 300 is a single piece.
[0049] Gas distributor 300 has a gas deflection surface 302 and a
gas distributor face 304. Gas deflection surface 302 provides a
pathway for cleaning gases during a chamber clean process. Cleaning
gases are directed to the chamber walls instead of the substrate
support member located directly below the gas distributor. The gas
distributor 300 is connected to a chamber wall at a proximal
portion 306. During a CVD process, a deposition gas is supplied to
the gas distributor 300 at the proximal end 308. A rim 338 extends
annularly around proximal end 308. This deposition gas flows
through gas distributor 300, exiting at apertures 310, and onto a
substrate position on the substrate support member.
[0050] Apertures 310 are disposed on the gas distributor face 304
at a step 312, a raised surface. Step 312 can form an oval level
or, more preferably, a circular level on gas distributor face 304
having a predetermined diameter. The diameter can range from about
0.01 inches to about 3.00 inches. Step 312 can have a vertical
height in a range of about 0.60 inches to about 0.75 inches, and
have a slope in a range of about 90 deg to about 15 deg. Step 312
improves gas distribution of gas distributor 300. In particular,
the deposition gas can be dispersed further out to the periphery of
the substrate support member as a result of step 312. Decreasing
the slope of step 312 further disperse the gas towards the outside.
While gas distributor 300 shows an embodiment of the step and
apertures, other embodiments are possible, for example as described
in U.S. application Ser. No. 11/075527, filed Mar. 7, 2005, the
full disclosure of which has been previously incorporated herein by
reference.
[0051] In specific embodiments, gas distributor 300 can have 4, 6,
8, or more apertures 310. These apertures 310 are evenly
distributed along the circumference of step 312 or, alternatively,
weighted to a particular portion thereof. The placement and number
of apertures 310 can be tuned for a specific application to achieve
uniform distribution of deposition gas unto the substrate.
Likewise, the diameter of apertures 310 can also be tuned. The
diameter can be in the range of about 0.005 inches to about 0.250
inches. In a specific embodiment, the diameter of apertures 310 are
0.060 inches.
[0052] A baffle 320 is formed so as to deflect a clean gas. Baffle
320 includes gas deflection surface 302. Gas deflection surface 302
includes a concave surface 322 and a portion of a convex surface
346. Gas deflection surface 302 and baffle 320 are rotationally
symmetric about an axis 314. Concave surface 322 is formed to fit a
radius 324. Concave surface 322 includes an upper portion 328 and a
lower portion 329, so that concave surface 322 extends from an
upper boundary 322a to a lower boundary 322b. An arc 326 of radius
324 extends from upper boundary 322a to lower boundary 322b. Gas
deflection surface 302 transitions from concave surface 322 to
convex surface 346 at lower boundary 322b. Convex surface 346 is
formed in a flange 330.
[0053] Convex surface 346 is formed to match an arcuate path of a
radius 348. Convex surface 346 and concave surface 322 are arranged
so that gas deflection surface 302 transitions from concave surface
322 to convex surface 346 at lower boundary 322b with a continuous
surface. The intersection of concave surface 322 with convex
surface 346 is at a slight angle to provide a smooth continuous
surface transition as lower boundary 322b. In an alternate
embodiment, this smooth transition is accomplished by setting the
slope of the convex and concave surfaces to zero at lower boundary
322 so that the transition from the concave surface to the convex
surface is completely smooth as the angle of the concave surface is
matched to the angle of the convex surface at the transition. In
yet another embodiment, the intersection of the concave surface
with the convex surface is at a substantial angle to provide a
continuous transition surface with a slight bend at the transition
from the concave surface to the convex surface.
[0054] Gas distributor 300 includes a maximum width 340 across the
gas distributor. Maximum width 340 corresponds to a diameter across
convex surface 346. Maximum width 346 has a range from about 1.4 to
2.0 inches, and is typically about 1.7 inches.
[0055] With respect to the lower surface of the gas distributor, a
smooth transition is formed at the transition between gas
distributor face 304 and convex surface 346, similar to the smooth
transition from concave surface 322 to convex surface 346. Flange
330 has a thickness 342. Thickness 342 corresponds to a distance
equal to twice radius 348.
[0056] FIG. 3B is a cross-sectional view of a gas distributor
positioned in a semiconductor processing chamber according to an
embodiment of the present invention. Gas distributor 300 is
designed to be positioned in the semiconductor gas processing
chamber. As positioned in the chamber, gas deflection surface 302
corresponds to an upper exposed surface of the gas distributor, and
gas distributor face 304 corresponds to a lower exposed surface of
the gas distributor. Gas distributor 300 is supported by an annular
structure 360. Annular structure 360 has a channel 362 formed
therein to deliver the deposition gas. Rim 338 engages annular
structure 360 and is adapted to form a seal with annular structure
360. Threads 336 mate with corresponding threads on annular
structure 360. A shoulder 334 is located on the gas distributor
adjacent to upper portion 328 of the concave gas deflection
surface. Shoulder 334 mates with a corresponding surface formed in
an annular structure 360. Annular structure 360 has an outer
surface 364 which matches upper portion 328 of the concave gas
deflection surface so as to provide a smooth surface transition
from the annular support structure to the gas deflection surface.
Top vent 246 includes an annular opening 368 into the chamber.
[0057] The baffle acts to divert the flow of the clean gas from a
first direction to a second direction which is transverse to the
first direction. Top vent 246 directs the clean gas downward in a
first direction 350 along upper portion 328 of the gas deflection
surface. Concave surface 322 directs the clean gas horizontally in
a second direction 352 along lower portion 329 of concave surface
322, and second direction 352 is transverse to first direction 350.
Concave surface 322 also directs the clean gas horizontally in a
third direction 354, and third direction 354 is transverse to first
direction 350. Concave portion 322 comprises about 90% of an
exposed surface area of gas deflection surface 302. Gas deflection
surface 302 extends along second direction 352 for a distance less
that thickness 342 of flange 330.
[0058] FIG. 3C is a top view of a gas distributor as shown in FIG.
3A according to an embodiment of the present invention. As can be
seen in FIG. 3C, many of the structures shown in FIG. 3A are
annular and rotationally symmetric. Outer edge 332 of gas
distributor 300 has a circular shape. Flange 330 has an annular
shape. Lower boundary 322b has a circular shape. Concave surface
322 of the gas deflection surface has an annular shape. Upper
boundary 322a of concave surface 322 has a circular shape. Shoulder
334 has an annular shape. Threads 336 have an annular shape. Rim
338 has an annular shape. Axis 318 is shown for reference.
[0059] With reference to FIGS. 3A and 3C, it will be appreciated
that concave surface 322 comprises a portion of a first torus, and
convex surface 346 comprises a portion of a second torus. Concave
surface 322 is defined by radius 324 rotated about axis 314 to
define the first torus. Convex surface 346 is defined by radius 348
rotated about axis 318 to define the second torus. Thus, lower
boundary 322b is a boundary defined by the intersection of two
toric surfaces adapted to mate with a smooth transition from the
first toric surface to the second toric surface. In alternate
embodiments, either the concave surface or the convex surface, or
both, are defined by non-toric shapes, for example shapes defiled
by elliptical curved surfaces, cubic splines and the like. Also,
stepped surfaces using several small steps can be used to define
the concave and convex surfaces.
[0060] FIG. 4 is a cross-sectional view of a gas distributor 400
with a truncated gas deflection surface according to an embodiment
of the present invention. A baffle 420 has a gas deflection surface
402 formed thereon. Gas deflection surface 402 includes the concave
surface 322 as described above, including upper portion 328 and
lower portion 329. Gas deflection surface 402 ends with annular
edge 482. A flange 430 includes an cylindrical outer surface 432. A
maximum width 440 across the baffle corresponds to the diameter
across cylindrical outer surface 432. Annular edge 482 connects gas
deflection surface 402 with outer cylindrical surface 432. Annular
edge 482 is rounded to fit a short radius of curvature and
comprises a convex toric surface. An annular edge 484 connects gas
distributor face 304 with cylindrical outer surface 432. A
thickness 442 of flange 430 corresponds to a distance across flange
430 from lower portion 329 to an annular portion of gas distributor
face 304 near annular edge 484.
[0061] FIG. 5 is a cross-sectional view of a gas distributor 500
with an annular flat transition portion 564 extending between
concave and convex gas deflection surfaces according to an
embodiment of the present invention. The concave surface and convex
surfaces are toric surfaces as described above. Gas distributor 500
includes a baffle 520 with a gas deflection surface 502 formed
thereon. Concave portion 522 comprises about 75% of an exposed
surface area of gas deflection surface 502. Gas distributor 500
includes a gas distributor face 504 adapted to distribute a
deposition gas with apertures 310 and a step 312 as described
above. Gas deflection surface 502 includes concave surface 322,
annular flat transition portion 564 and an upper portion of a
convex surface 546. Concave surface 322 extends between upper
boundary 322a and lower boundary 322b and includes upper portion
328 and lower portion 329 as described above. Annular flat
transition portion 564 provides a smooth transition from concave
surface 322 to convex surface 546.
[0062] Convex surface 546 includes a radius 548 and other
attributes of the gas distributor. Convex surface 546 extends
between an upper boundary 546a and a lower boundary 546b. Convex
surface 546 includes an outer edge 532. A maximum width 540 across
the gas distributor corresponds do a diameter across the
distributor define by outer edge 532. Annular flat transition
portion 564 extends between lower boundary 322b of concave surface
322 and upper boundary 546a of convex surface 546. Lower boundary
546b is positioned between convex surface 546 and gas distributor
face 504. A flange 530 includes annular flat transition portion 564
and convex surface 546. A flange thickness 542 corresponds to a
distance equal to twice the radius 548.
[0063] Dimensions of annular flat transition portion are related to
other dimensions of the gas distributor. For example, the distance
of annular flat transition portion 564 along maximum width 540 is
no more than about 10% of the maximum width as shown in FIG. 5. In
some embodiments the distance of the annular flat transition
portion is no more than about 20% of the maximum width. In other
embodiments, the distance of the flat annular transition portion is
no more than about 5% of the maximum width. In some embodiments,
there is no flat annular transition portion, for example as shown
above in FIGS. 3A to 3C, as the concave portion transitions
directly to the convex potion along the boundary between the convex
portion and the concave portion.
[0064] FIG. 6 is a flow chart illustrating a method 600 of
processing a wafer with a decreased season time and Al
contamination, in accordance with an embodiment of the present
invention. A clean chamber step 610 cleans the chamber with the gas
baffle as described above, for example as shown in FIGS. 3A to 3C.
The amount of time required to clean the chamber will depend on the
nature of the semiconductor processes employed, the season time,
the clean gas and/or gasses used and the temperature. A typical
clean time ranges from about 2 minutes to 7 minutes, and is often
from 3 to 5 minutes, for example 3 to 4 minutes. A season chamber
step 620 seasons the chamber with a deposition gas to provide a
protective coating as described above, for example silane used to
deposit a protective SiO.sub.2 layer. The amount of time to season
the chamber is less than 60 seconds, for example from about 25 to
60 seconds, often from about 25 to 45 seconds, and preferably from
about 25 to 35 seconds. An insert wafer step 630 inserts a
semiconductor wafer into the chamber so that the wafer is
positioned as described above. An apply HDP-CVD gap-fill layer to
wafer step 640 applies a gap fill layer to the wafer with an
HDP-CVD process as described above. The HDP-CVD process can be any
one of a lower power process, a medium power process, and a high
power process. The gap fill process is typically applied for about
60 seconds. A thickness of the gap fill layer applied with the gap
fill process is often from about 40000 A (400 nm) to 8000 A (800
nm) thick, for example to 4000 A (400 nm) to 6000 A (400 nm) thick,
and typically about 5000 A (500 nm) thick. Although the exact
amount of Aluminum contamination in the gap-fill layer of the
processed wafer will depend upon the exact parameters selected, the
number of Al atoms is typically less than 2.times.10.sup.12 atoms
per square centimeter, for example from about 0.3.times.10.sup.12
to 2.0.times.10.sup.12 atoms per square centimeter, and can be from
about 0.3.times.10.sup.12 to 1.5.times.10.sup.12 atoms per square
centimeter, and preferably from about 0.3.times.10.sup.12 to
1.0.times.10.sup.12 atoms per square centimeter. A remove wafer
step 650 removes the wafer from the chamber so that the wafer can
be subject to additional process steps outside the chamber. After
remove wafer step 650, the chamber is cleaned and steps 610 to 650
are repeated for additional wafers.
[0065] Any combination of chamber clean time, season time, and
process power can be selected to provide a desired level of metal
atom contamination. As season time is increased, metal atom
contamination decreases and the season time is selected to provide
metal ion contamination that is below a predetermined maximum
tolerated amount. To optimize wafer throughput, one selects the
shortest season time that provides metal atom contamination below
the predetermined amount. For example, a season time of 30 seconds
and can provide a metal ion contamination of 1.2.times.10.sup.12 Al
atoms per square centimeter that is below a maximum tolerated
amount of 1.5.times.10.sup.12 Al atoms per square centimeter. With
a season time of 30 seconds, the total time to clean the chamber,
place the wafer in the chamber, process the wafer in the chamber
and remove the wafer from the chamber corresponds to a throughput
of at least about 8 wafers per hour.
[0066] It should be appreciated that the specific steps illustrated
in FIG. 6 provide a particular method of processing a wafer
according to an embodiment of the present invention. Other
sequences of steps may also be performed according to alternative
embodiments. For example, alternative embodiments of the present
invention may perform the steps outlined above in a different
order. Moreover, the individual steps illustrated in FIG. 6 may
include multiple sub-steps that may be performed in various
sequences as appropriate to the individual step. Furthermore,
additional steps may be added or removed depending on the
particular applications. One of ordinary skill in the art would
recognize many variations, modifications, and alternatives.
[0067] 3. Experimental Results
[0068] Preliminary testing with embodiments of the present
invention show that significant improvements can be achieved,
including reduced Al contamination and increase throughput of
wafers processed in the chamber. Testing with embodiments of the
present invention typically included single piece AlN (aluminum
nitride) gas distributors formed from a mold and NF.sub.3 clean
gas, although other gas distributor materials, for example Alumina,
and clean other gases, for example F.sub.2, can be used. As an
example, preliminary testing with embodiments using a high power
process has shown that Al contamination can be reduced from
1.3.times.10.sup.13 atoms per square centimeter on the substrate
with a season time of 120 s for a prior baffle to as in FIG. 1 to
Al contamination of 1.2.times.10.sup.12 atoms per square centimeter
on the substrate with a season time of 30 s for a baffle as in FIG.
3. The thickness of the coatings tested was about 8000 A.
Therefore, an approximate order of magnitude decrease in Al
contamination is achieved while decreasing the season time from 120
s to 30 s with a high power process. A decrease in season time from
120 s to 30 s can result in an increase in wafers processed per
hour from about 7 wafers to 8 wafers as the chamber is seasoned
several times during the processing of a wafer.
[0069] FIG. 7 shows a comparison of clean end-points for a prior
gas distributor as in FIG. 1 and a gas distributor as in FIG. 3
according to an embodiment of the present invention. The season
time for each tested embodiment was the same. A "clean signal" in
arbitrary units versus time is shown in FIG. 7. Clean signals 710
and 712 are shown for the prior distributor and the tested
embodiment, respectively. The clean signals were measured with
Fourier Transform Infrared spectroscopy (FTIR). The clean signals
for the two distributors are nearly identical and show no
substantial differences. Therefore, embodiments of the present
invention can provide cleaning characteristics that are nearly
identical with the tested prior baffle so that the tested
embodiment is compatible with systems that use the prior baffle,
and the tested embodiment can be provided as an upgrade to systems
that use the prior baffle.
[0070] FIG. 8 shows a comparison of Al contamination in a
processing chamber with a prior gas distributor as in FIG. 1 versus
a gas distributor as in FIG. 3 according to an embodiment of the
present invention. The season time was set to 120 s for the
processes used for both baffles to provide an assessment of the
effect of the baffle on Al contamination. Process A was a medium
power process having a power of approximately 10 kW, and process
gases included NF.sub.3, He, SiH.sub.4 and O.sub.2 gases. As
process A used NF.sub.3 and medium power, chemical reactions
associated with fluorine are believed to be the primary cause of
chamber contamination. Medium power processes generally use power
of approximately Process B was a high power process with a power of
approximately 18 kW and process gases that included NF.sub.3,
H.sub.2, SiH.sub.4 and O.sub.2. As process B was a high power
process, thermal reactions, for example sublimation, are believed
to be the primary cause of chamber contamination. With respect to
process A, the tested prior baffle provided Al contamination of
approximately 200.times.10.sup.10 Al atoms per square centimeter
and the tested embodiment provided approximately 70.times.10.sup.10
Al atoms per square centimeter. The thickness of the coating
applied with process A was about 4000 A. With respect to process B,
the prior baffle provided Al contamination of approximately
1000.times.10.sup.10 Al atoms per square centimeter and the tested
embodiment provided approximately 30.times.10.sup.10 Al atoms per
square centimeter. The thickness of the coating applied with
process B was about 8000 A. Thus, the tested embodiment provided
approximately a factor of three improvement with the medium power
process and approximately a factor of thirty improvement with the
high power process.
[0071] The above-described arrangements of apparatus and methods
are merely illustrative of applications of the principles of this
invention and many other embodiments and modifications may be made
without departing from the spirit and scope of the invention as
defined in the claims. The scope of the invention should,
therefore, be determined not with reference to the above
description, but instead should be determined with reference to the
appended claims along with their full scope of equivalents.
* * * * *