U.S. patent application number 11/601293 was filed with the patent office on 2007-03-22 for fast gas switching plasma processing apparatus.
This patent application is currently assigned to Lam Research Corporation. Invention is credited to Rajinder Dhindsa, Zhisong Huang, Eric H. Lenz, S.M. Reza Sadjadi, Jose Tong Sam.
Application Number | 20070066038 11/601293 |
Document ID | / |
Family ID | 39402006 |
Filed Date | 2007-03-22 |
United States Patent
Application |
20070066038 |
Kind Code |
A1 |
Sadjadi; S.M. Reza ; et
al. |
March 22, 2007 |
Fast gas switching plasma processing apparatus
Abstract
A plasma chamber with a plasma confinement zone with an
electrode is provided. A gas distribution system for providing a
first gas and a second gas is connected to the plasma chamber,
wherein the gas distribution system can substantially replace one
gas in the plasma zone with the other gas within a period of less
than 1 s. A first frequency tuned RF power source for providing
power to the electrode in a first frequency range is electrically
connected to the at least one electrode wherein the first frequency
tuned RF power source is able to minimize a reflected RF power. A
second frequency tuned RF power source for providing power to the
plasma chamber in a second frequency range outside of the first
frequency range wherein the second frequency tuned RF power source
is able to minimize a reflected RF power.
Inventors: |
Sadjadi; S.M. Reza;
(Saratoga, CA) ; Huang; Zhisong; (Fremont, CA)
; Sam; Jose Tong; (Pleasanton, CA) ; Lenz; Eric
H.; (Pleasanton, CA) ; Dhindsa; Rajinder; (San
Jose, CA) |
Correspondence
Address: |
BEYER WEAVER LLP
P.O. BOX 70250
OAKLAND
CA
94612-0250
US
|
Assignee: |
Lam Research Corporation
|
Family ID: |
39402006 |
Appl. No.: |
11/601293 |
Filed: |
November 17, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10835175 |
Apr 30, 2004 |
|
|
|
11601293 |
Nov 17, 2006 |
|
|
|
Current U.S.
Class: |
438/478 ;
118/715; 118/723R; 156/345.28; 156/345.33; 438/5 |
Current CPC
Class: |
H01J 37/32091 20130101;
H01J 37/3244 20130101; H01J 37/32449 20130101; H01J 37/32155
20130101 |
Class at
Publication: |
438/478 ;
438/005; 156/345.28; 156/345.33; 118/715; 118/723.00R |
International
Class: |
H01L 21/00 20060101
H01L021/00; C23F 1/00 20060101 C23F001/00; H01L 21/306 20060101
H01L021/306; C23C 16/00 20060101 C23C016/00; H01L 21/20 20060101
H01L021/20 |
Claims
1. A plasma wafer processing tool, comprising: a plasma chamber
with a plasma confinement zone with a volume and at least one
electrode; a gas distribution system for providing a first gas and
a second gas, wherein the gas distribution system can substantially
replace one of the first gas and the second gas in the plasma zone
with the other of the first gas and the second gas within a period
of less than 1 s, wherein a first plasma formed in the plasma zone
from the first gas provides a first impedance load and wherein a
second plasma formed in the plasma zone from the second gas
provides a second impedance load different than the first impedance
load; a first frequency tuned RF power source for providing power
to the at least one electrode in a first frequency range wherein
the first frequency tuned RF power source is able to receive
reflected RF power and tune an output RF frequency to minimize the
reflected RF power; and a second frequency tuned RF power source
for providing power to the plasma chamber in a second frequency
range outside of the first frequency range wherein the second
frequency tuned RF power source is able to receive reflected RF
power and tune an output RF frequency to minimize the reflected RF
power.
2. The plasma wafer processing tool, as recited in claim 1, wherein
the first frequency tuned RF power source is able to provide a
first frequency to impedance match the first impedance load and a
second frequency to impedance match the second impedance load,
wherein the first frequency is different than the second
frequency.
3. The plasma wafer processing tool, as recited in claim 2, wherein
the second frequency tuned RF power source is able to provide a
third frequency to impedance match the first impedance load and a
fourth frequency to impedance match the second impedance load,
wherein the fourth frequency is different than the first, second,
and third frequency.
4. The plasma wafer processing tool, as recited in claim 3, wherein
the gas distribution system can substantially replace the first gas
or the second gas in the plasma zone with the other of the first
gas or the second gas within a period of less than 200 ms.
5. The plasma wafer processing tool, as recited in claim 4, wherein
the plasma chamber further comprises: a substrate support for
supporting a wafer within the plasma chamber; and a chamber top
spaced apart less than 3 cm. from the substrate support.
6. The plasma wafer processing tool, as recited in claim 5, further
comprising confinement rings spaced apart between the chamber top
and substrate support.
7. The plasma wafer processing tool, as recited in claim 6, wherein
interiors of the confinement rings, the substrate support, and
chamber top define the plasma zone.
8. The plasma wafer processing tool, as recited in claim 7, wherein
the first frequency turned RF power source and the second frequency
tuned RF power source tune the output RF frequency over a range of
less than 1 MHz.
9. The plasma wafer processing tool, as recited in claim 1, wherein
the gas distribution system comprises: a first gas passage and a
second gas passage adapted to be in fluid communication with a
first gas line; a third gas passage and a fourth gas passage
adapted to be in fluid communication with a second gas line, the
first and third gas passages being adapted to supply gas to the
vacuum chamber, and the second and fourth gas passages being
adapted to supply gas to a by-pass line; a first fast switching
valve arranged along the first gas passage; a second fast switching
valve arranged along the second gas passage; a third fast switching
valve arranged along the third gas passage; a fourth fast switching
valve arranged along the fourth gas passage; the first and fourth
fast switching valves being adapted to receive signals to open
while the second and third fast switching valves are closed so that
the first gas is supplied to the vacuum chamber via the first gas
line and the first and third gas passages while the second gas is
supplied to the by-pass line via the second gas line and the second
and fourth gas passages; and the second and third fast switching
valves being adapted to receive signals to open while the first and
fourth fast switching valves are closed so that the second gas is
supplied to the vacuum chamber via the second gas line and the
third gas passage while the first gas is supplied to the by-pass
line via the first gas line and the second gas passage.
10. The plasma wafer processing tool, as recited in claim 9,
wherein the gas distribution system further comprises: a first flow
restrictor adapted to be arranged along the first gas line upstream
of the first and second fast switching valves; and a second flow
restrictor adapted to be arranged along the second gas line
upstream of the third and fourth fast switching valves; wherein the
first and second flow restrictors are adapted to maintain an
approximately constant gas pressure in a region of the first and
second gas lines upstream of and proximate the first and second
flow restrictors.
11. The plasma wafer processing tool, as recited in claim 10,
wherein the first gas line has a volume between the first flow
restrictor and the first and second fast switching valves of less
than about 10 cm.sup.3, and the second gas line has a volume
between the second flow restrictor and the third and fourth fast
switching valves of less than about 10 cm.sup.3.
12. The plasma wafer processing tool, as recited in claim 9,
further wherein the gas distribution system further comprises: a
third flow restrictor adapted to be arranged along the first gas
passage downstream of the first fast switching valve; a fourth flow
restrictor adapted to be arranged along the second gas passage
downstream of the second fast switching valve; a fifth flow
restrictor adapted to be arranged along the third gas passage
downstream of the third fast switching valve; and a sixth flow
restrictor adapted to be arranged along the fourth gas passage
downstream of the fourth fast switching valve; wherein the third,
fourth, fifth and sixth flow restrictors are adapted to maintain an
approximately constant gas pressure in a region of the first,
second, third and fourth gas passages upstream of and proximate the
respective first, second, third, fourth, fifth and sixth flow
restrictors.
13. The plasma wafer processing tool, as recited in claim 9,
further comprising a controller which is operable to control the
opening and closing of the first, second, third and fourth fast
switching valves.
14. The plasma wafer processing tool, as recited in claim 9,
wherein the first, second, third and fourth fast switching valves
can be opened and/or closed within a period of less than about 100
ms after receiving a signal.
15. The plasma wafer processing tool, as recited in claim 1,
further comprising a gas distribution member having an inner zone
and outer zone, which are flow insulated from each other.
16. The plasma wafer processing tool, as recited in claim 15,
wherein the gas distribution system comprises: a gas supply system,
which provides the first gas and the second gas; a flow control
system in fluid communication with the gas supply system, which
splits a flow of the first gas into an inner zone flow of the first
gas and an outer zone flow of the first gas and which splits a flow
of the second gas into an inner zone flow of the second gas and an
outer zone flow of the second gas; and a switching section, which
is in fluid connection between the flow control system and the
inner zone and outer zone of the gas distribution member, and
wherein the switching section switches flow to the inner zone of
the gas distribution member between the inner zone flow of the
first gas and the inner zone of the second gas and wherein the
switching section switches flow to the outer zone of the gas
distribution member between the outer zone flow of the first gas
and the outer zone flow of the second gas.
17. The plasma wafer processing tool, as recited in claim 16,
further comprising a by-pass line, wherein the switching section
also switches the inner zone flow of the first gas, the inner zone
of the second gas, the outer zone flow of the first gas, and the
outer zone flow of the second gas to the by-pass line.
18. The plasma wafer processing tool, as recited in claim 17,
wherein the flow control system further comprising a tuning gas
source in fluid connection to at least one of the first gas inner
zone flow or first gas outer zone flow after the flow of the first
gas is split into the inner zone flow of the first gas and the
outer zone flow of the first gas.
19. A plasma processing apparatus, comprising: a plasma processing
chamber including a showerhead electrode assembly having the inner
and outer zones and an interior volume of about 1/2 liter to 4
liters; the gas distribution system in fluid communication with the
inner and outer zones of the showerhead electrode assembly, wherein
the gas distribution system being operable to substantially replace
a first process gas or a second process gas in the plasma
confinement zone with the other of the first process gas or the
second process gas within a period of less than about 1 s,
comprising: a gas supply system, which provides the first process
gas and the second process gas; a flow control system in fluid
communication with the gas supply system, which splits a flow of
the first process gas into an inner zone flow of the first process
gas and an outer zone flow of the first process gas and which
splits a flow of the second process gas into an inner zone flow of
the second process gas and an outer zone flow of the second process
gas; and a switching section, which is in fluid connection between
the flow control system and the inner zone and outer zone of the
gas distribution member, and wherein the switching section switches
flow to the inner zone of the gas distribution member between the
inner zone flow of the first process gas and the inner zone of the
second process gas and wherein the switching section switches flow
to the outer zone of the gas distribution member between the outer
zone flow of the first process gas and the outer zone flow of the
second process gas; a first frequency tuned RF power source for
providing power to the plasma processing apparatus in a first
frequency range wherein the first frequency tuned RF power source
is able to receive reflected RF power and tune an output RF
frequency to minimize the reflected RF power; and a second
frequency tuned RF power source for providing power to the plasma
processing apparatus in a second frequency range outside of the
first frequency range wherein the second frequency tuned RF power
source is able to receive reflected RF power and tune an output RF
frequency to minimize the reflected RF power.
20. The plasma processing apparatus, as recited in claim 19,
further comprising a by-pass line, wherein the switching section
also switches the inner zone flow of the first process gas, the
inner zone of the second process gas, the outer zone flow of the
first process gas, and the outer zone flow of the second process
gas to the by-pass line.
21. The plasma processing apparatus, as recited in claim 20,
wherein the flow control system further comprising a tuning gas
source in fluid connection to at least one of the first process gas
inner zone flow or first process gas outer zone flow after the flow
of the first process gas is split into the inner zone flow of the
first process gas and the outer zone flow of the first process
gas.
22. The plasma processing apparatus, as recited in claim 21,
wherein the first frequency tuned RF power source is able to
provide a first frequency to impedance match a first impedance load
of a plasma formed from the first process gas and a second
frequency to impedance match a second impedance load of a plasma
formed from the second plasma gas, wherein the first frequency is
different than the second frequency and wherein the second
frequency tuned RF power source is able to provide a third
frequency to impedance match the first impedance load and a fourth
frequency to impedance match the second impedance load, wherein the
fourth frequency is different than the first, second, and third
frequency.
23. A method of processing a semiconductor structure in a plasma
processing chamber, comprising: a) supplying a first process gas
into the plasma processing chamber while diverting a second process
gas to a bypass-line, the plasma processing chamber containing a
semiconductor substrate including at least one layer and a
patterned resist mask overlying the layer; b) energizing the first
process gas to produce a first plasma with a first impedance load
and (i) etching at least one feature in the layer or (ii) forming a
polymer deposit on the mask; c) frequency tuning a first RF power
source to a first frequency to match the first impedance load; d)
frequency tuning a second RF power source to a second frequency
different than the first frequency to match the first impedance
load; e) switching the flows of the first and second process gases
so that the second process gas is supplied into the plasma
processing chamber while diverting the first process gas to the
by-pass line, the first process gas being substantially replaced in
a plasma confinement zone of the plasma processing chamber by the
second process gas within a period of less than about 1 s; f)
energizing the second process gas to produce a second plasma with a
second impedance load different from the first impedance load and
(iii) etching the at least one feature in the layer or (iv) forming
a polymer deposit on the layer and the mask; g) frequency tuning
the first RF power source to a third frequency different than the
first and second frequencies to match the second impedance load; h)
frequency tuning the second RF power source to a fourth frequency
different than the first, second, and third frequencies to match
the second impedance load; i) switching the flows of the first and
second process gases so that the first process gas is supplied into
the plasma processing chamber while diverting the second process
gas to the by-pass line, the second process gas being substantially
replaced in the plasma confinement zone of the plasma processing
chamber by the first process gas within a period of less than about
1 s; and j) repeating b)-i) a plurality of times with the
substrate.
24. The method, as recited in claim 23, wherein the periods of less
than about 1 s is less than 200 ms.
25. The method, as recited in claim 23, wherein the polymer deposit
is formed to a maximum thickness of less than about 100 angstroms
after repeating a)-i) a plurality of times with the substrate.
26. The method, as recited in claim 23, further comprising:
splitting a flow of the first process gas into an inner zone flow
and an outer zone flow, wherein the supplying the first process gas
into the plasma processing chamber provides the inner zone flow to
an inner zone of the processing chamber and the outer zone flow to
an outer zone of the processing chamber.
27. The method, as recited in claim 26, further comprising
providing a tuning gas to at least one of the inner zone flow of
the first process gas and the outer zone flow of the first process
gas, wherein the tuning gas is provided after the splitting of the
flow of the first process gas.
28. The method of claim 27, wherein the first plasma etches the at
least one feature in the layer, and the second plasma forms the
deposit on the layer and the mask, the deposit repairing striations
in the mask.
29. The method of claim 23, wherein the plasma confinement zone has
a volume of about 1/2 liter to about 4 liters.
30. The method, as recited in claim 23, wherein: the first layer is
of SiO.sub.2; the mask is a UV-resist mask; the first process gas
comprises a mixture of C.sub.4F.sub.8, O.sub.2 and argon and the
first plasma etches the layer; and the second process gas comprises
a mixture of CH.sub.3F, argon, and optionally O.sub.2 and the
second plasma forms the polymer deposit on the feature and the
mask.
31. The method, as recited in claim 23, wherein the frequency
tuning the first RF power source to a first frequency to match the
first impedance load, and the frequency tuning the first RF power
source to a third frequency to match the second impedance load use
a matchbox to partially match the first impedance load and third
impedance load and use frequency tuning to provide a final match of
the first impedance load and second impedance load.
Description
RELATED APPLICATIONS
[0001] This is a Continuation-In-Part of co-pending prior U.S.
application Ser. No. 10/835,175 entitled "GAS DISTRIBUTIONS SYSTEM
HAVING FAST GAS SWITCHING CAPABILITIES", filed on Apr. 30, 2004,
which is hereby incorporated by reference.
BACKGROUND
[0002] Semiconductor structures are processed in plasma processing
apparatuses including a plasma processing chamber, a gas source
that supplies process gas into the chamber, and an energy source
that produces plasma from the process gas. Semiconductor structures
are processed in such apparatuses by techniques including dry
etching processes, deposition processes, such as chemical vapor
deposition (CVD), physical vapor deposition, or plasma-enhanced
chemical vapor deposition (PECVD) of metal, dielectric and
semiconductor materials and resist stripping processes. Different
process gases are used for these processing techniques, as well as
processing different materials of semiconductor structures.
SUMMARY
[0003] To achieve the foregoing and in accordance with the purpose
of the present invention, a plasma wafer processing tool is
provided. A plasma chamber with a plasma confinement zone with a
volume and at least one electrode is provided. A gas distribution
system for providing a first gas and a second gas is connected to
the plasma chamber, wherein the gas distribution system can
substantially replace one of the first gas and the second gas in
the plasma zone with the other of the first gas and the second gas
within a period of less than 1 s, wherein a first plasma formed in
the plasma zone from the first gas provides a first impedance load
and wherein a second plasma formed in the plasma zone from the
second gas provides a second impedance load different than the
first impedance load. A first frequency tuned RF power source for
providing power to the at least one electrode in a first frequency
range is electrically connected to the at least one electrode
wherein the first frequency tuned RF power source is able to
receive reflected RF power and tune an output RF frequency to
minimize the reflected RF power. A second frequency tuned RF power
source for providing power to the plasma chamber in a second
frequency range outside of the first frequency range wherein the
second frequency tuned RF power source is able to receive reflected
RF power and tune an output RF frequency to minimize the reflected
RF power.
[0004] In another manifestation of the invention a plasma
processing apparatus is provided. A plasma processing chamber
including a showerhead electrode assembly having the inner and
outer zones and an interior volume of about 1/2 liter to 4 liters
is provided. A gas distribution system is in fluid communication
with the inner and outer zones of the showerhead electrode
assembly, wherein the gas distribution system is operable to
substantially replace a first process gas or a second process gas
in the plasma confinement zone with the other of the first process
gas or the second process gas within a period of less than about 1
s. The gas distribution comprises a gas supply system, which
provides the first process gas and the second process gas, a flow
control system in fluid communication with the gas supply system,
which splits a flow of the first process gas into an inner zone
flow of the first process gas and an outer zone flow of the first
process gas and which splits a flow of the second process gas into
an inner zone flow of the second process gas and an outer zone flow
of the second process gas, and a switching section, which is in
fluid connection between the flow control system and the inner zone
and outer zone of the gas distribution member, wherein the
switching section switches flow to the inner zone of the gas
distribution member between the inner zone flow of the first
process gas and the inner zone of the second process gas and
wherein the switching section switches flow to the outer zone of
the gas distribution member between the outer zone flow of the
first process gas and the outer zone flow of the second process
gas. A first frequency tuned RF power source for provides power to
the plasma processing apparatus in a first frequency range wherein
the first frequency tuned RF power source is able to receive
reflected RF power and tune an output RF frequency to minimize the
reflected RF power. A second frequency tuned RF power source for
provides power to the plasma processing apparatus in a second
frequency range outside of the first frequency range wherein the
second frequency tuned RF power source is able to receive reflected
RF power and tune an output RF frequency to minimize the reflected
RF power.
[0005] In another manifestation of the invention, a method of
processing a semiconductor structure in a plasma processing chamber
is provided. a) A first process gas is supplied into the plasma
processing chamber while diverting a second process gas to a
bypass-line, the plasma processing chamber containing a
semiconductor substrate including at least one layer and a
patterned resist mask overlying the layer. b) The first process gas
is energized to produce a first plasma with a first impedance load
and (i) etching at least one feature in the layer or (ii) forming a
polymer deposit on the mask. c) A first RF power source is
frequency tuned to a first frequency to match the first impedance
load. d) A second RF power source is frequency tuned to a second
frequency different than the first frequency to match the first
impedance load. e) The flows of the first and second process gases
are switched so that the second process gas is supplied into the
plasma processing chamber while diverting the first process gas to
the by-pass line, the first process gas being substantially
replaced in a plasma confinement zone of the plasma processing
chamber by the second process gas within a period of less than
about 1 s. f) The second process gas is energized to produce a
second plasma with a second impedance load different from the first
impedance load and (iii) etching the at least one feature in the
layer or (iv) forming a polymer deposit on the layer and the mask.
g) The first RF power source is frequency tuned to a third
frequency different than the first and second frequencies to match
the second impedance load. h) The second RF power source is
frequency tuned to a fourth frequency different than the first,
second, and third frequencies to match the second impedance load.
i) The flows of the first and second process gases are switched so
that the first process gas is supplied into the plasma processing
chamber while diverting the second process gas to the by-pass line,
the second process gas being substantially replaced in the plasma
confinement zone of the plasma processing chamber by the first
process gas within a period of less than about 1 s. j) Steps b)-i)
are repeated a plurality of times with the substrate.
[0006] These and other features of the present invention will be
described in more details below in the detailed description of the
invention and in conjunction with the following figures.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0007] The present invention is illustrated by way of example, and
not by way of limitation, in the figures of the accompanying
drawings and in which like reference numerals refer to similar
elements and in which:
[0008] FIG. 1 is a sectional view of an exemplary embodiment of a
plasma processing apparatus that preferred embodiments of the gas
distribution system can be used with.
[0009] FIG. 2 illustrates a preferred embodiment of the gas
distribution system.
[0010] FIG. 3 depicts a preferred embodiment of a gas supply
section of the gas distribution system.
[0011] FIG. 4 depicts a preferred embodiment of a flow control
section of the gas distribution system.
[0012] FIG. 5 depicts a first preferred embodiment of a gas
switching section of the gas distribution system.
[0013] FIG. 6 depicts a second preferred embodiment of the gas
switching section of the gas distribution system.
[0014] FIG. 7 depicts a third preferred embodiment of the gas
switching section of the gas distribution system.
DETAILED DESCRIPTION
[0015] Plasma processing apparatuses for processing semiconductor
materials, such as semiconductor devices formed on semiconductor
substrates, e.g., silicon wafers, include a plasma processing
chamber and a gas distribution system that supplies process gas
into the plasma processing chamber. The gas distribution system can
distribute gas to a single zone or multiple zones across the
surface of a substrate during plasma processing. The gas
distribution system can include flow controllers to control the
flow ratio of the same or different process gas, or gas mixture, to
the zones, thereby allowing in-process adjustment of
across-substrate uniformity of gas flow and gas composition.
[0016] Although multiple-zone gas distribution systems can provide
improved flow control as compared to a single-zone system, it may
be desirable to provide such systems with an arrangement that
allows substrate processing operations in which the gas composition
and/or the gas flow can be changed within a short period of
time.
[0017] A gas distribution system is provided for supplying
different gas compositions and/or flow ratios to a chamber. In a
preferred embodiment, the gas distribution system is adapted to be
in fluid communication with an interior of a vacuum chamber, such
as a plasma processing chamber of a plasma processing apparatus,
and provide the capability of supplying different gas chemistries
and/or gas flow rates to the vacuum chamber during processing
operations. The plasma processing apparatus can be a low-density,
medium-density or high-density plasma reactor including an energy
source that uses RF energy, microwave energy, magnetic fields, or
the like to produce plasma. For example, the high-density plasma
can be produced in a transformer coupled plasma (TCP.TM.) reactor,
also known as an inductively coupled plasma reactor, an
electron-cyclotron resonance (ECR) plasma reactor, a
capacitive-type discharge, or the like. Exemplary plasma reactors
that preferred embodiments of the gas distribution system can be
used with include Exelan.TM. plasma reactors, such as the 2300
Excelan.TM. plasma reactor, available from Lam Research
Corporation, located in Fremont, Calif. During plasma etching
processes, multiple frequencies can be applied to a substrate
support incorporating an electrode and an electrostatic chuck.
Alternatively, in dual-frequency plasma reactors, different
frequencies can be applied to the substrate support and an
electrode, such as a showerhead electrode, spaced from the
substrate.
[0018] A preferred embodiment of the gas distribution system can
supply a first gas into the interior of a vacuum chamber, such as a
plasma processing chamber, via a single zone or multiple zones,
preferably at least an inner zone and an outer zone of a gas
distribution member adjacent to an exposed surface of a substrate
to be processed. The inner and outer zones are radially spaced, and
preferably, flow insulated, from each other in the plasma
processing chamber. The gas distribution system can simultaneously
divert a second gas that is different from the first gas to a
vacuum chamber by-pass line. The by-pass line can be in fluid
communication with a vacuum pump, or the like. In a preferred
embodiment, the first gas is a first process gas and the second gas
is a different process gas. For example, the first gas can be a
first etch gas chemistry or deposition gas chemistry, and the
second gas can be a different etch gas chemistry or deposition gas
chemistry. The gas distribution system can simultaneously provide
different controlled flow rates of the first gas to the inner zone
and the outer zone, respectively, while the second gas is diverted
to the by-pass line, and vice versa. By diverting one of the gases
to the by-pass line, change over of the gas supplied to the vacuum
chamber can be achieved within a short period of time.
[0019] The gas distribution system includes switching devices that
allow gas switching, or gas change over, in a short period of time
between first and second gases supplied to an interior of a vacuum
chamber that includes a single zone or includes multiple zones. For
multiple-zone systems, the gas distribution system can supply the
first gas to the inner zone and outer zone while the second gas is
diverted to the by-pass line, and then switch the gas distributions
within a short period of time so that the second gas is supplied to
the inner zone and outer zone while the first gas is diverted to
the by-pass line. The gas distribution system can alternately
supply the first and second gases into the interior of the vacuum
chamber, each for a desired period of time to allow quick change
over between different processing operations that use different gas
chemistries, e.g., alternating steps of a method of processing a
semiconductor device. In a preferred embodiment, the method steps
can be different etch steps, e.g., a faster etch step, such as a
main etch, and a relatively slower etch step, such as an over etch
step; an etch step and a material deposition step; or different
material deposition steps that deposit different materials onto a
substrate.
[0020] In a preferred embodiment of the gas distribution system, a
volume of a gas composition in a confined region within a vacuum
chamber, preferably a plasma confinement zone, can be replaced
(i.e., flushed out) by another gas composition introduced into the
vacuum chamber within a short period of time. Such gas replacement
preferably can be achieved in less than about 1 s, more preferably
within less than about 200 ms, by providing valves having a fast
switching capability in the gas distribution system. The plasma
confinement zone can have a gas volume of about 1/2 liter to about
4 liters for a plasma processing chamber for processing 200 mm or
300 mm wafers. The plasma confinement zone can be defined by a
stack of confinement rings, such as disclosed in commonly-owned
U.S. Pat. No. 5,534,751, which is hereby incorporated by reference
in its entirety.
[0021] FIG. 1 depicts an exemplary semiconductor material plasma
processing apparatus 10 that embodiments of the gas distribution
system 100 can be used with. The apparatus 10 comprises a vacuum
chamber or plasma processing chamber 12 having an interior
containing a substrate support 14 on which a substrate 16 is
supported during plasma processing. The substrate support 14
includes a clamping device, preferably an electrostatic chuck 18,
which is operable to clamp the substrate 16 on the substrate
support 14 during processing. The substrate can be surrounded by
focus rings and/or edge rings, ground extensions or other parts,
such as parts disclosed in commonly-owned U.S. Patent Application
Publication No. US 2003/0029567, which is incorporated herein by
reference in its entirety.
[0022] In a preferred embodiment, the plasma processing chamber 12
includes a plasma confinement zone having a volume of about 12
liter to about 4 liters, preferably about 1 liter to about 3
liters. For example, the plasma processing chamber 12 can include a
confinement ring arrangement, such as disclosed in commonly-owned
U.S. Pat. No. 5,534,751, which is incorporated herein by reference
in its entirety, to define the plasma confinement zone. The gas
distribution system can replace such a volume of gas in the plasma
confinement zone with another gas within a period of less than
about 1 s, preferably in less than about 200 ms, without
substantial back diffusion. A confinement mechanism, such as
confinement rings 120, can limit the fluid communication from the
plasma volume to portions of the interior of the plasma processing
chamber 12 that are outside of the plasma volume.
[0023] The substrate 16 may include a base material, such as a
silicon wafer; an intermediate layer of a material that is to be
processed, e.g., etched, over the base material; and a masking
layer over the intermediate layer. The intermediate layer may be of
a conductive, dielectric, or semiconductive material. The masking
layer can be patterned photoresist material having an opening
pattern for etching desired features, e.g., holes, vias and/or
trenches, in the intermediate layer and/or one or more other
layers. The substrate can include additional layers of conductive,
dielectric or semiconductive materials between the base layer and
the masking layer, depending on the type of semiconductor device
formed on the base material.
[0024] Exemplary dielectric materials that can be processed are,
for example, doped silicon oxide, such as fluorinated silicon
oxide; un-doped silicon oxide, such as silicon dioxide; spin-on
glass; silicate glasses; doped or un-doped thermal silicon oxide;
and doped or un-doped TEOS deposited silicon oxide. Such dielectric
materials can overlie a conductive or semiconductive layer, such as
polycrystalline silicon; metals, such as aluminum, copper,
titanium, tungsten, molybdenum and their alloys; nitrides, such as
titanium nitride; and metal suicides, such as titanium silicide,
tungsten silicide and molybdenum silicide.
[0025] The exemplary plasma processing apparatus 10 shown in FIG. 1
includes a showerhead electrode assembly having a support plate 20
forming a wall of the plasma chamber, and a showerhead 22 attached
to the support plate. A baffle assembly is located between the
showerhead 22 and the support plate 20 to uniformly distribute
process gas to a backside 28 of the showerhead. The baffle assembly
can include one or more baffle plates. In the embodiment, the
baffle assembly includes baffle plates 30A, 30B, and 30C. Open
plenums 48A, 48B and 48C are defined between the baffle plates 30A,
30B and 30C; and between the baffle plate 30C and showerhead 22.
The baffle plates 30A, 30B and 30C and showerhead 22 include
through passages for flowing process gas into the interior of
plasma processing chamber 12.
[0026] A first frequency tuned RF power source 104 is controllably
connected to a controller 500 and provides power to the showerhead
electrode 22 through a first mechanical match box 106. The first
frequency tuned RF power source 104 provides a variable frequency,
which in this embodiment ranges from 1.7 MHz to 2.2 MHz, so that 2
MHz lies within the variable frequency range The first frequency
tuned RF power source is formed to receive and measure output power
and reflected RF power and to vary the frequency in the frequency
range of 1.7 MHz to 2.2 MHz to minimize reflected RF power from the
first frequency tuned RF power source 104.
[0027] A second frequency tuned RF power source 108 is controllably
connected to a controller 500 and provides power to the showerhead
electrode 22 through a second mechanical match box 110. The second
frequency tuned RF power source 108 provides a variable frequency,
which in this embodiment ranges from 26.7 MHz to 27.2 MHz, so that
27 MHz lies within the variable frequency range. The second
frequency tuned RF power source is formed to receive and measure
output power and reflected RF power and to vary the frequency in
the frequency range of 26.7 MHz to 27.2 MHz to minimize reflected
RF power from the second frequency tuned RF power source 108.
[0028] A third frequency tuned RF power source 112 is controllably
connected to a controller 500 and provides power to the showerhead
electrode 22 through a third mechanical match box 114. The third
frequency tuned RF power source 112 provides a variable frequency,
which in this embodiment ranges from 59.7 MHz to 60.2 MHz, so that
60 MHz lies within the variable frequency range. The third
frequency tuned RF power source 112 is formed to receive and
measure output power and reflected RF power and to vary the
frequency in the frequency range of 59.7 MHz to 60.2 MHz to
minimize reflected RF power from the third frequency tuned RF power
source 112.
[0029] In this example, the first, second, and third frequency
tuned RF power sources vary the frequency over a range of 0.5 MHz
to provide RF tuning. In other embodiments, the frequency tuned RF
power sources vary the frequency over a range of less than 2 MHz.
More preferably, the frequency tuned RF power sources vary the
frequency over a range of less than 1 MHz. The tuning range should
be large enough to minimize reflected power and yet small enough to
allow fast tuning.
[0030] In the embodiment, the plenum between the plate 20 and the
baffle plate 30A and the plenums 48A, 48B and 48C between the
baffle plates 30A, 30B and 30C are divided into an inner zone 42
and an outer zone 46 by seals 38a, 38b, 38c and 38d, such as
O-rings. The inner zone 42 and outer zone 46 can be supplied
process gas having different respective gas chemistries and/or flow
rates by the gas distribution system 100, preferably under control
of the controller 500. Gas is supplied from an inner zone gas
supply 40 into the inner zone 42, and gas is supplied from an outer
zone gas supply 44 into an annular channel 44a and then into the
outer zone 46. The process gas flows through the passages in the
baffle plates 30A, 30B and 30C and the showerhead 22 and into the
interior of the plasma processing chamber 12.
[0031] In other preferred embodiments, the plasma processing
apparatus 10 can include a gas injector system for injecting
process gas into the plasma processing chamber. For example, the
gas injector system can have a configuration as disclosed in
commonly-owned U.S. patent application Ser. No. 09/788,365, U.S.
patent application Ser. No. 10/024,208, U.S. Pat. No. 6,013,155, or
U.S. Pat. No. 6,270,862, each of which is incorporated herein by
reference in its entirety.
[0032] The process gas is energized into the plasma state in the
plasma processing chamber 12 by a power source, such as an RF
source driving electrode 22, or a power source driving an electrode
in the substrate support 14. The RF power applied to the electrode
22 can be varied when different gas compositions are supplied into
the plasma processing chamber 12, preferably within a time period
of less than about 1 s, more preferably less than about 200 ms. The
change in gas compositions can change the load or impedance from
the gas. The first, second, and third RF power sources 104, 108,
112 may have mechanical impedance matching devices, but such
devices may not be fast enough to match the changing impedance when
different gas compositions are provided for time periods less than
about 1 s. Therefore, the first, second, and third RF power sources
have variable frequencies and are able to measure output and
reflected RF power and to vary the frequency to minimize reflected
RF power. The minimizing the reflected RF power matches the
impedance of the load from the plasma in the processing chamber
with the RF power sources through a matchbox.
[0033] FIG. 2 shows a preferred embodiment in which the gas
distribution system 100 includes a gas supply section 200, a flow
control section 300, and a gas switching section 400 in fluid
communication with each other. The gas distribution system 100
preferably also includes a controller 500 (FIG. 1), which is
connected in control communication to control operation of the gas
supply section 200, flow control section 300 and gas switching
section 400.
[0034] In the gas distribution system 100, the gas supply section
200 can supply different gases, such as first and second process
gases, to the flow control section 300 via respective first and
second gas lines 235, 245. The first and second gases can have
different compositions and/or gas flow rates from each other.
[0035] The flow control section 300 is operable to control the flow
rate, and optionally also to adjust the composition, of different
gases that can be supplied to the switching section 400. The flow
control section 300 can provide different flow rates and/or
chemistries of the first and second gases to the switching section
400 via gas passages 324, 326 and 364, 366, respectively. In
addition, the flow rate and/or chemistry of the first gas and/or
second gas that is supplied to the plasma processing chamber 12
(while the other gas is diverted to by-pass line 50, which can be
in fluid communication with a vacuum pumping system, such as
between a turbo pump and a roughing pump) can be different for the
inner zone 42 and the outer zone 46. Accordingly, the flow control
section 300 can provide desired gas flows and/or gas chemistries
across the substrate 16, thereby enhancing substrate processing
uniformity.
[0036] In the gas distribution system 100, the switching section
400 is operable to switch from the first gas to the second gas
within a short period of time to allow the first gas to be replaced
by the second gas in a single zone or multiple zones, e.g., the
inner zone 42 and the outer zone 46, while simultaneously diverting
the first gas to the by-pass line, or vice versa. The gas switching
section 400 preferably can switch between the first and second
gases without the occurrence of undesirable pressure surges and
flow instabilities in the flow of either gas. If desired, the gas
distribution system 100 can maintain a substantially constant
sequential volumetric flow rate of the first and second gases
through the plasma processing chamber 12.
[0037] FIG. 3 shows a preferred embodiment of the gas supply
section 200 of the gas distribution system 100. The gas supply
section 200 is preferably connected to the controller 500 to
control operation of flow control components, such as valves and
flow controllers, to allow control of the composition of two or
more gases that can be supplied by the gas supply section 200. In
the embodiment, the gas supply section 200 includes multiple gas
sources 202, 204, 206, 208, 210, 212, 214 and 216, each being in
fluid communication with the first gas line 235 and the second gas
line 245. As such, the gas supply section 200 can supply many
different desired gas mixtures to the plasma processing chamber 12.
The number of gas sources included in the gas distribution system
100 is not limited to any particular number of gas sources, but
preferably includes at least two different gas sources. For
example, the gas supply section 200 can include more than or less
than the eight gas sources included in the embodiment shown in FIG.
3. For example, the gas supply section 200 can include two, three,
four, five, ten, twelve, sixteen, or more gas sources. The
different gases that can be provided by the respective gas sources
include individual gases, such as O.sub.2, Ar, H.sub.2, Cl.sub.2,
N.sub.2 and the like, as well as gaseous fluorocarbon and/or
fluorohydrocarbon compounds, such as CF.sub.4, CH.sub.3F and the
like. In one preferred embodiment, the plasma processing chamber is
an etch chamber and the gas sources 202-216 can supply Ar, O.sub.2,
N.sub.2, Cl.sub.2, CH.sub.3, CF.sub.4, C.sub.4F.sub.8 and CH.sub.3F
or CHF.sub.3 (in any suitable order thereof). The particular gases
supplied by the respective gas sources 202-216 can be selected
based on the desired process that is to be performed in the plasma
processing chamber 12, e.g., particular dry etching and/or material
deposition processes. The gas supply section 200 can provide broad
versatility regarding the choice of gases that can be supplied for
performing etching processes and/or material deposition
processes.
[0038] The gas supply section 200 preferably also includes at least
one tuning gas source to adjust the gas composition. The tuning gas
can be, e.g., O.sub.2, an inert gas, such as argon, or a reactive
gas, such as a fluorocarbon or fluorohydrocarbon gas, e.g.,
C.sub.4F.sub.8. In the embodiment shown in FIG. 3, the gas supply
section 200 includes a first tuning gas source 218 and a second
tuning gas source 219. As described below, the first tuning gas
source 218 and second tuning gas source 219 can supply tuning gas
to adjust the composition of the first and/or second gas supplied
to the gas switching section 400.
[0039] In the embodiment of the gas supply section 200 shown in
FIG. 3, a flow control device 240 preferably is disposed in each of
the gas passages 222, 224, 226, 228, 230, 232, 234 and 236 in fluid
communication with the gas sources 202, 204, 206, 208, 210, 212,
214 and 216, respectively, and also in the gas passages 242, 244 in
fluid communication with the first tuning gas source 218 and the
second tuning gas source 219, respectively. The flow control
devices 240 are operable to control the flow of the gas supplied by
the associated gas sources 202-216 and 218, 219. The flow control
devices 240 preferably are mass flow controllers (MFCs).
[0040] In the embodiment shown in FIG. 3, valves 250, 252 are
located along the gas passages downstream of each of the gas
sources 202-216. The valves 250, 252 can be selectively opened or
closed, preferably under control of the controller 500, to allow
different gas mixtures to be flowed to the first gas line 235
and/or the second gas line 245. For example, by opening the valves
252 associated with one or more of the gas sources 202-216 (while
the remaining valves 252 associated with the other ones of the gas
sources 202-216 are closed), a first gas mixture can be supplied to
the first gas line 235. Likewise, by opening the valves 250
associated with one or more of the other gas sources 202-216 (while
the remaining valves 250 associated with the other ones of the gas
sources 202-216 are closed), a second gas mixture can be supplied
to the second gas line 245. Accordingly, various mixtures and mass
flow rates of the first and second gases can be provided to the
first gas line 235 and the second gas line 245 by controlled
operation of the gas supply section 200.
[0041] In a preferred embodiment, the gas supply section 200 is
operable to provide a continuous flow of the first and second gases
via the first gas line 235 and the second gas line 245,
respectively. The first gas or the second gas is flowed to the
plasma processing chamber 12 while the other gas is diverted to the
by-pass line. The by-pass line can be connected to a vacuum pump,
or the like. By continuously flowing both of the first and second
gases, the gas distribution system 100 can achieve rapid change
over of the gas flow.
[0042] FIG. 4 shows a preferred embodiment of the flow control
section 300 of the gas distribution system 100. The flow control
section 300 includes a first flow control section 305 in fluid
communication with the first gas line 235 from the gas supply
section 200, and a second flow control section 315 in fluid
communication with the second gas line 245 from the gas supply
section 200. The flow control section 300 is operable to control
the ratio of the first gas supplied to the inner zone 42 and outer
zone 46, respectively, while the second gas is diverted to the
by-pass line, and to control the ratio of the second gas supplied
to the inner zone 42 and outer zone 46, respectively, while the
first gas is diverted to the by-pass line. The first flow control
section 305 divides the flow of the first gas introduced at the
first gas line 235 into two separate outlet flows of the first gas,
and the second flow control section 315 divides the flow of the
second gas introduced at the second gas line 245 into two separate
outlet flows of the second gas. The first flow control section 305
includes first and second gas passages 324, 326 in fluid
communication with the inner zone 42 and outer zone 46,
respectively, via the switching system 400, and the second flow
control section 315 includes first and second gas passages 364, 366
in fluid communication with the inner zone 42 and outer zone 46,
respectively, via the switching system 400.
[0043] In a preferred arrangement, the first flow control section
305 and the second flow control section 315 each include at least
two flow restrictors. Each flow restrictor preferably has a fixed
restriction size for gas flow through it. The flow restrictors are
preferably orifices. The flow restrictors restrict gas flow and
maintain an approximately constant gas pressure in a region of the
gas passages upstream of and proximate the orifices. Each of the
first flow control section 305 and the second flow control section
315 preferably includes a network of orifices, e.g., two, three,
four, five or more orifices, each preferably having a different
cross-sectional restriction size, e.g., a different diameter or a
different cross-sectional area. The restriction sizes of the
orifices are smaller than the cross-sectional areas of the other
portions of the gas flow path of the gas distribution system 100.
The orifices are preferably sonic orifices. The gas flows are
preferably operated at the critical flow regime in the flow control
section 300 so that the flow conductance of a given orifice is
determined solely by its restriction size and upstream pressure. As
the flow conductance of an orifice increases, the pressure drop
across the orifice to achieve a given flow rate through the orifice
decreases.
[0044] In the embodiment shown in FIG. 4, the first and second flow
control sections 305, 315 each include five orifices 330, 332, 334,
336 and 338. For example, the orifices 330, 332, 334, 336 and 338
can have relative restriction sizes, e.g., diameters, of one, two,
four, eight, and sixteen, respectively. Accordingly, when gas flow
occurs through all five orifices 330-338, the four orifices 330-336
have approximately the same total conductance as that of the single
orifice 338. Alternatively, up to three of the four orifices
330-336 can be opened to provide different ratios of the total
conductance of the orifices 330-336 as compared to the conductance
of the orifice 338, in order to supply different ratios of the
first gas flow and the second gas flow to the inner zone 42 and the
outer zone 46.
[0045] Another embodiment can include a different number of
orifices, e.g., a total of two orifices; including the orifice 338
and a second orifice that replaces the multiple orifices 330-336.
The second orifice preferably has the same restriction size as the
orifice 338. In such embodiment, the flow ratio of the first gas
and/or second gas supplied to the inner zone 42 and the outer zone
46 is approximately 1:1.
[0046] Valves 320 preferably are located upstream of each of the
respective orifices 330-338 to control the flow of the first and
second gases to the orifices. For example, in the first flow
control section 305 and/or the second flow control section 315, one
or more of the valves 320 can be opened to allow flow of the first
gas and/or second gas to one or more of the associated orifice(s)
330-336, while the other valve 320 is opened to allow flow of the
first gas and/or the second gas to the orifice(s) 338.
[0047] In the first flow control section 305, the orifices 330-336
are in fluid communication with the gas passage 322. The gas
passage 322 is divided into the first and second gas passages 324,
326, which are in fluid communication with the gas switching
section. A pair of valves 320 is located in the first and second
gas passages 324, 326 to control flow of the first gas flowed
through one or more of the orifices 330-336 of the first flow
control section 305 to the inner zone 42 and/or the outer zone 46.
In an alternative embodiment, the pair of valves 320 located along
the gas passages 324, 326 can be replaced by a single, four-way
valve.
[0048] In the first flow control section 305, the orifice 338 is
arranged along the gas passage 319. The gas passage 319 is divided
into gas passages 331, 333, which are in fluid communication with
the first and second gas passages 324, 326, respectively. A pair of
valves 320 is located in the gas passages 331, 333 to control flow
of the first gas flowed through the orifice 338 to the first and
second gas passages 324, 326. In an alternative embodiment, the
pair of valves 320 located along the gas passages 331, 333 can be
replaced by a single, four-way valve.
[0049] In the second flow control section 315, a pair of valves 320
is located along the first and second gas passages 364, 366 to
control flow of the second gas flowed through one or more of the
orifices 330-336 to the inner zone 42 and the outer zone 46 of the
plasma processing chamber. In an alternative embodiment, the pair
of valves 320 located along the gas passages 364, 366 can be
replaced by a single, four-way valve.
[0050] In the second flow control section 315, the orifice 338 is
arranged along the gas passage 359. The gas passage 359 is divided
into gas passages 372, 374, which are in fluid communication with
the first and second gas passages 364, 366, respectively. A pair of
valves 320 is located in the gas passages 372, 374 to control flow
of the second gas flowed through the orifice 338 to the first
and/or second gas passages 364, 366. In an alternative embodiment,
the pair of valves 320 located along the gas passages 372, 374 can
be replaced by a single four-way valve.
[0051] The orifices 330-338 are included in the flow control
section 300 to prevent pressure surges and flow instabilities in
the gas flow when the gas distribution system 100 changes the gas
flowed into the plasma processing chamber 12 from the first gas to
the second gas, and vice versa.
[0052] In the embodiment shown in FIG. 4, the gas passage 242 of
the first tuning gas source 218 (FIG. 3) is arranged to supply the
first tuning gas to the first gas passage 324 and/or second gas
passage 326 of the first flow control section 305 to adjust the
first gas composition. The gas passage 244 of the second tuning gas
source 219 (FIG. 3) is arranged to supply the second tuning gas to
the first gas passage 364 and/or second gas passage 366 of the
second flow control section 315 to adjust the second gas
composition. The first and second tuning gases can be the same
tuning gas or different tuning gases.
[0053] A flow control device 340, preferably an MFC, is arranged
along the gas passage 242. Valves 320 are located along the gas
passages 337, 339 to control flow of the first tuning gas into the
gas passage 326, 324, respectively. In an alternative embodiment,
the pair of valves 320 located along the gas passages 337, 339 can
be replaced by a single, four-way valve.
[0054] A flow control device 340, preferably an MFC, is arranged
along the gas passage 244. Valves 320 are located along the gas
passages 376, 378 to control flow of the second tuning gas into the
gas passages 366, 364, respectively. In an alternative embodiment,
the pair of valves 320 located along the gas passages 376, 378 can
be replaced by a single, four-way valve.
[0055] In the embodiment of the flow control section 300 shown in
FIG. 4, the first flow control section 305 and the second flow
control section 315 include the same components arranged in the
same configuration. However, in other preferred embodiments of the
gas distribution system 100, the first and second flow control
sections 305, 315 can have different components and/or different
configurations from each other. For example, the first and second
flow control sections 305, 315 can include different numbers of
orifices and/or orifices with different restriction sizes from each
other.
[0056] In the gas distribution system 100, the gas switching system
400 is in fluid communication with the flow control section 300,
and with the interior of the vacuum chamber and the by-pass line to
which the first and second gases are flowed. A first preferred
embodiment of the gas switching system 400 is depicted in FIG. 5.
The gas switching system 400 can alternately supply first and
second gases to both the inner zone 42 and the outer zone 46 of the
plasma processing chamber 12. The gas switching system 400 is in
fluid communication with the first gas passage 324 and the second
gas passage 326 of the first flow control section 305, and with the
first gas passage 364 and the second gas passage 366 of the second
flow control section 315. An orifice 430 is arranged along each of
the gas passages 324, 326, 364 and 366 to prevent undesirable
pressure surges during change over of the first and second
gases.
[0057] The first gas passage 324 of the first flow control section
305 is divided into gas passages 448, 450; the second gas passage
326 of the first flow control section 305 is divided into gas
passages 442, 444; the first gas passage 364 of the second flow
control section 315 is divided into gas passages 452, 454; and the
second gas passage 366 of the second flow control section 315 is
divided into gas passages 456, 458. In the embodiment, the gas
passage 442 is in fluid communication with the outer zone 46 of the
plasma chamber 12, the gas passage 448 is in fluid communication
with the inner zone 42 of the plasma processing chamber 12, and the
gas passage 444 provides a by-pass line. The gas passage 456 is in
fluid communication with the gas passage 442 to the outer zone 46.
The gas passage 452 is in fluid communication with the gas passage
448 to the inner zone 42. The gas passages 450, 454 and 458 are in
fluid communication with the gas passage 444 to the by-pass
line.
[0058] A valve 440 is arranged along each of the gas passages 442,
444, 448, 450, 452, 454, 456, and 458. In an alternative
embodiment, each of the pairs of valves 440 located along the gas
passages 442, 444; 448, 450; 452, 454; and 456, 458 can be replaced
by a single, four-way valve. The valves 440 can be selectively
opened and closed, preferably under control of the controller 500,
to supply the first or second gas to the chamber, while
simultaneously diverting the other gas to the by-pass line.
[0059] For example, to supply the first gas to the inner zone 42
and the outer zone 46 of the plasma processing chamber 12 and
divert the second gas to the by-pass line, the valves 440 along the
gas passages 442, 448 and 454, 458 are opened, while the valves 440
along the gas passages 444, 450 and 452, 456 are closed. To switch
the gas flow so that the second gas is supplied to the inner zone
42 and the outer zone 46 of the plasma processing chamber 12, while
the first gas is diverted to the by-pass line, the valves 440 along
the gas passages 444, 450 and 452, 456 are opened, while the valves
440 along the gas passages 442, 448 and 454, 458 are closed. In
other words, a first group of valves 440 is opened and a second
group of valves 440 is closed to supply the first gas to the plasma
processing chamber 12, and then the same first group of valves is
closed and the same second group of valves 440 is opened to change
the gas flow to supply the second gas to the plasma processing
chamber.
[0060] In the gas switching system 400, the valves 440 are
fast-switching valves. As used herein, the term "fast-switching
valve" means a valve that can be opened or closed within a short
period of time, preferably less than about 100 ms, more preferably
less than about 50 ms, after receiving a signal from the controller
500 to open or close. The valves 440 are preferably electronically
controlled and actuated by receiving a signal from the controller
500 to open or close. A suitable "fast-switching valve" that can be
used in the gas switching system 400 is valve model number
FSR-SD-71-6.35, available from Fujikin of America, located in Santa
Clara, Calif.
[0061] Accordingly, the gas switching system 400 can supply the
first gas, e.g., to the interior of the vacuum chamber while
diverting the second gas to the by-pass line, and then, preferably
under control of the controller 500, quickly switch these gas flows
and supply the second gas to the vacuum chamber while diverting the
first gas to the by-pass line. The amount of time that the first
gas or second gas is supplied to the vacuum chamber before the
gases are switched can be controlled by the controller 500. The
volume of the gas passages 324, 326, 364, and 366 between the
associated orifices 430 and the valves 440 preferably is less than
about 10 cm.sup.3. As explained above, the gas distribution system
can be used with a plasma processing chamber including a plasma
confinement zone to replace a gas volume of about 1/2 liter to
about 4 liters within a period of less than about 1 s, more
preferably less than about 200 ms, to thereby stabilize the
system.
[0062] A gas switching system 1400 according to a second preferred
embodiment is depicted in FIG. 6. In the gas switching system 1400,
a valve 440 and an orifice 430, which is located downstream of the
valve 440 are arranged along each of the gas passages 442-458.
Otherwise, the gas switching system 1400 can have the same
configuration as the gas switching system 400. The orifices 430
prevent undesirable pressure surges during switching of gases. In
an alternative embodiment, each of the pairs of valves 440 located
along the gas passages 442, 444; 448, 450; 452, 454; and 456, 458
can be replaced by a single, four-way valve.
[0063] A gas switching system 2400 according to a third preferred
embodiment is depicted in FIG. 7. In this embodiment, the gas
switching system 2400 is in fluid communication with a first gas
passage 405 and a second gas passage 415. The first and second gas
passages 405, 415 can be, e.g., a first gas outlet and a second gas
outlet, respectively, of a flow control section that, unlike the
flow control section 300 shown in FIG. 4, does not include both
inner and outer zone gas outlets. An orifice 430 is located along
each of the first gas passage 405 and second gas passage 415. The
first gas passage 405 is divided into gas passages 422, 424, and
the second gas passage 445 is divided into gas passages 426, 428.
The gas passages 422 and 426 are in fluid communication with an
interior of a vacuum chamber, and the gas passages 424 and 428 are
in fluid communication with a by-pass line. A valve 440 is located
along each of the gas passages 422, 424 and 426, 428. In an
alternative embodiment, each of the pairs of valves 440 located
along the gas passages 422, 424; and 426, 428 can be replaced by a
single, four-way valve.
[0064] For example, to supply the first gas to the vacuum chamber
and simultaneously route the second gas to the by-pass line, the
valves 440 along the fluid passages 422 and 428 are opened and the
valves 440 along the gas passages 424 and 426 are closed. To switch
the gas flows so that the second gas is supplied to the vacuum
chamber and the first gas is diverted to the by-pass line, the
valves 440 along the fluid passages 424 and 426 are opened and the
valves 440 along the fluid passages 422 and 428 are closed.
[0065] In another preferred embodiment of the gas switching system,
the embodiment shown in FIG. 7 can be modified by removing the
orifices 430 arranged in the first gas passage 405 and second gas
passage 415 upstream of the valves 440, and instead arranging a
orifice in each of the gas passages 422, 424, 426 and 428
downstream of the associated valves 440.
[0066] Preferred embodiments of the gas distribution system 100 can
be used to supply different gas chemistries and/or flow rates to
the plasma processing chamber 12 to perform various etching and/or
deposition processes. For example, the gas distribution system 100
can supply process gases to a plasma processing chamber to etch
features in a silicon oxide, such as an SiO.sub.2 layer protected
by an overlying mask, such as a UV resist mask. The SiO.sub.2 layer
can be formed on a semiconductor wafer, such as a silicon wafer,
having a diameter of 200 mm or 300 mm. The features can be, e.g.,
vias and/or trenches. During such etching processes, it is
desirable to deposit a polymer on portions of the mask to repair
striations, e.g., cracks or fissures, in the mask (i.e., to fill
the striations) so that features etched in the SiO.sub.2 have their
desired shape, e.g., vias have a round cross-section. If striations
are not repaired, they can eventually reach the layer underlying
the mask and in effect be transferred to that layer during etching.
Also, a polymer can be deposited on the sidewalls of the
features.
[0067] It has been determined, however, that the thickness of the
polymer deposited on the sidewalls and the base of etched features
affects the etch rate. In anisotropic etching processes, polymer
deposited on the bottom of the feature is substantially removed
during etching. However, if the polymer becomes too thick on the
sidewalls and/or on the base, the etch rate of SiO.sub.2 is
decreased, and may be stopped completely. Polymer may also flake
off of surfaces if it becomes too thick. Accordingly, the amount of
time that the gas mixture for forming the polymer deposit on the
mask and features is supplied into the plasma processing chamber is
preferably controlled to thereby control the thickness of the
polymer deposit formed on the SiO.sub.2 layer, while also providing
sufficient repair and protection of the mask. During etching of the
SiO.sub.2 layer, polymer is periodically removed from the mask.
Accordingly, the polymer is preferably deposited on the mask
between periods of etching of the SiO.sub.2 layer to ensure that
sufficient repair and protection of the mask is achieved.
[0068] The gas distribution system 100 can be used to supply
process gas into a plasma processing chamber to etch SiO.sub.2
protected by an overlying mask, e.g., a UV resist mask, with
control of the thickness of polymer deposited on the features, and
with repair and protection of the mask. The gas switching system of
the gas distribution system 100 is operable to allow a first
process gas used to etch the SiO.sub.2 to be supplied into the
plasma processing chamber for a first period of time while a second
gas mixture used to form the polymer deposit is diverted to a
bypass line, and then to quickly switch the gas flows so that the
second gas mixture is supplied into the plasma processing chamber
to form the polymer deposit while the first gas mixture is supplied
to the by-pass line. Preferably, the first gas mixture supplied to
a plasma confinement zone of the plasma processing chamber is at
least substantially replaced with the second gas mixture within a
period of less than about 1 s, more preferably less than about 200
ms. The plasma confinement zone preferably has a volume of about
1/2 liter to about 4 liters.
[0069] The first gas mixture used to etch SiO.sub.2 can contain,
e.g., a fluorocarbon species, such as C.sub.4F.sub.8, O.sub.2, and
argon. The flow ratio of C.sub.4F.sub.8/O.sub.2/argon can be, e.g.,
20/10/500 sccm. Power is provided with at a combination of
frequencies of 60 MHz, 27 MHz, and 2 MHz, at powers that can range
from 50 to 5000 W. The second gas mixture used to form a polymer
deposit can contain, e.g., a fluorohydrocarbon species, such as
CH.sub.3F, and argon. The flow ratio of CH.sub.3F/argon can be,
e.g., 15/500 sccm. The second gas mixture can optionally also
include O.sub.2. Power is provided at a combination of frequencies
of 60 MHz, 27 MHz, and 2 MHz at powers that can range from 50 to
5000 W. For a capacitive-coupled plasma etch reactor for processing
200 mm or 300 mm wafers, the chamber pressure can be, e.g., 70-90
mTorr. The first gas mixture is preferably flowed into the plasma
processing chamber for about 5 seconds to about 20 seconds each
time it is introduced into the chamber (while the second gas is
diverted to the by-pass line), and the second gas mixture is
preferably flowed into the plasma processing chamber for about 1
second to about 3 seconds each time it is introduced into the
chamber (while the first gas is diverted to the by-pass line).
During etching of SiO.sub.2 on a substrate, the length of the
etching period and/or the polymer deposition period can be
increased or decreased within the preferred time periods. The
polymer deposit preferably reaches a maximum thickness of less than
about 100 angstroms during the etching process, which typically
lasts up to about 3 minutes. During etching, polymer can be
deposited on the mask to repair striations and provide mask
protection. Accordingly, the shape of the openings in the mask
preferably can be maintained during the etching process.
[0070] The first, second, and third mechanical match boxes 106,
110, 114 are used to provide gross impedance matching between the
first, second, and third frequency tuned RF power sources 104, 108,
112 and the load in the plasma processing chamber 12. The first,
second, and third mechanical boxes 106, 110, 114 are not able to
precisely match the quickly changing impedance load caused by the
quickly changing recipe. Therefore, the invention uses frequency
tuning provided by the first, second, and third frequency tuned RF
power sources 104, 108, 112 to quickly and precisely match the
quickly varying impedance of the load and the first, second, and
third mechanical match boxes 106, 110, 114 with the impedance of
the first, second, and third frequency tuned RF power sources 104,
108, 112.
[0071] Since the plasma conditions have to switch very rapidly
between deposition and shaping (etch), there are several hardware
features which have to work together. The gas volume must be small
to reduce gas transition time in the processing chamber. This is
achieved by making the plasma volume as small as possible using
confinement rings. Also, the RF generators have to be able to
rapidly tune in to the rapidly varying plasma conditions. This is
achieved by using electronically frequency tuned generators rather
than conventional mechanical match units. For best critical
dimension control (CD) and uniformity control main gases are split
and the ratio of center to edge gas flows are selectable. Finally,
a tuning gas is needed which can be the same or different from the
main gases and can be fed in a selectable flow to the edge or
center of the wafer. So, combination of all the aforementioned
hardware constitutes the overall performance desired for applied
processes put forth in this document.
[0072] While this invention has been described in terms of several
preferred embodiments, there are alterations, permutations, and
substitute equivalents, which fall within the scope of this
invention. It should also be noted that there are many alternative
ways of implementing the methods and apparatuses of the present
invention. It is therefore intended that the following appended
claims be interpreted as including all such alterations,
permutations, and substitute equivalents as fall within the true
spirit and scope of the present invention.
* * * * *