U.S. patent application number 10/013186 was filed with the patent office on 2002-05-02 for enhanced resist strip in a dielectric etcher using downstream plasma.
This patent application is currently assigned to Lam Research Corporation. Invention is credited to Marks, Jeffrey.
Application Number | 20020052114 10/013186 |
Document ID | / |
Family ID | 24150619 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020052114 |
Kind Code |
A1 |
Marks, Jeffrey |
May 2, 2002 |
Enhanced resist strip in a dielectric etcher using downstream
plasma
Abstract
A method and apparatus for performing a dielectric etch, etch
mask stripping, and etch chamber clean. A wafer is placed in an
etch chamber. A dielectric etch is performed on the wafer using an
in situ plasma generated by an in situ plasma device in the etch
chamber. The etch mask is stripped using a remote plasma generated
in a remote plasma device connected to the etch chamber. The wafer
is removed from the etch chamber and either the in situ plasma or
the remote plasma may be used to clean the etch chamber. In etch
chambers that do not use confinement rings, a heater may be used to
heat the etch chamber wall to provide improved cleaning.
Inventors: |
Marks, Jeffrey; (San Jose,
CA) |
Correspondence
Address: |
BEYER WEAVER & THOMAS LLP
P.O. BOX 778
BERKELEY
CA
94704-0778
US
|
Assignee: |
Lam Research Corporation
|
Family ID: |
24150619 |
Appl. No.: |
10/013186 |
Filed: |
December 7, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10013186 |
Dec 7, 2001 |
|
|
|
09539294 |
Mar 30, 2000 |
|
|
|
Current U.S.
Class: |
438/689 ;
257/E21.256 |
Current CPC
Class: |
H01J 2237/3342 20130101;
G03F 7/427 20130101; H01L 21/31138 20130101; H01J 37/32357
20130101; H01J 37/32082 20130101 |
Class at
Publication: |
438/689 |
International
Class: |
H01L 021/302; H01L
021/461 |
Claims
What is claimed is:
1. An apparatus for etching a dielectric layer disposed above a
substrate, comprising: a dielectric etch chamber; and a remote
plasma source connected to the dielectric chamber to provide a
reactant species to the interior of the dielectric etch
chamber.
2. The apparatus, as recited in claim 1, wherein the dielectric
etch chamber, comprises: a chamber wall; an etchant gas source to
provide an etchant gas within the chamber wall; and an in situ
plasma device for energizing the etchant gas into an in situ
plasma.
3. The apparatus, as recited in claim 2, wherein the etchant gas
comprises fluorocarbon.
4. The apparatus, as recited in claim 3, wherein the etchant gas
further comprises oxygen.
5. The apparatus, as recited in claim 4, wherein the remote plasma
source comprises: a remote plasma gas source; and a remote plasma
activation device, which energizes the gas from the remote plasma
gas source to a plasma.
6. The apparatus, as recited in claim 5, wherein the gas from the
remote plasma gas source is from the group consisting of oxygen,
nitrogen, and hydrogen.
7. The apparatus, as recited in claim 6, further comprising a
heater for heating the chamber wall to a temperature above
80.degree..
8. The apparatus, as recited in claim 6, further comprising a
plurality of confinement rings within the chamber wall and
surrounding a plasma region wherein the confinement rings are
spaced apart from each other.
9. The apparatus, as recited in claim 2, further comprising a
heater for heating the chamber wall to a temperature above
80.degree..
10. The apparatus, as recited in claim 2, further comprising a
plurality of confinement rings within the chamber wall and
surrounding a plasma region wherein the confinement rings are
spaced apart from each other.
11. A method for etching at least partially through a dielectric
layer disposed above a substrate, wherein part of said dielectric
layer is disposed below an etch mask and part of said dielectric
layer is not disposed below the etch mask, comprising the steps of:
placing the substrate in an etch chamber; flowing an etchant gas
into the etch chamber; creating an in situ plasma from the etchant
gas in the etch chamber; etching away parts of dielectric layer not
disposed below the etch mask; generating a remote plasma in a
remote plasma source; flowing the remote plasma into the etch
chamber; stripping away the etch mask, while the substrate is in
the etch chamber; and removing the substrate from the etch
chamber.
12. The method, as recited in claim 11, further comprising the step
of providing a plasma to clean the etch chamber after the step of
removing the substrate from the etch chamber.
13. The method, as recited in claim 12, wherein the etchant gas
further comprises oxygen.
14. The method, as recited in claim 13, further comprising the step
of discontinuing the flow of etchant gas into the etch chamber
before the step of flowing the remote plasma into the etch
chamber.
15. The method, as recited in claim 14, wherein the remote plasma
generated in the remote plasma source is from a gas from the group
consisting of oxygen, nitrogen, and hydrogen.
16. The method, as recited in claim 14, wherein the step of
providing a plasma clean to the etch chamber, comprises the step of
heating an etch chamber wall to a temperature above 80.degree..
17. The method, as recited in claim 16, wherein the step of
providing a plasma clean to the etch chamber, further comprises the
steps of: generating a remote plasma in the remote plasma source;
flowing the remote plasma into the etch chamber; and using the
remote plasma to remove residue from the heated chamber wall.
18. The method, as recited in claim 14, further comprising the step
of, confining the plasma within confinement rings, and wherein the
step of providing a plasma clean to the etch chamber, comprises the
steps of: flowing the etchant gas into the etch chamber; creating
an in situ plasma from the etchant gas in the etch chamber; and
using the in situ plasma from the etchant gas to remove residue
from the confinement rings.
19. The method, as recited in claim 12, wherein the step of
providing a plasma clean to the etch chamber, comprises the steps
of: heating an etch chamber wall to a temperature above
80.degree.generating a remote plasma in the remote plasma source;
flowing the remote plasma into the etch chamber; and using the
remote plasma to remove residue from the heated chamber wall.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to the manufacture of
semiconductor devices. More particularly, the present invention
relates to improved techniques for dielectric etching and resist
stripping.
[0002] In the manufacture of certain types of semiconductor
devices, dielectric layers may be etched using a plasma etching
system. Such plasma etching systems may be high density plasma
systems, such as inductive or ECR systems, or medium density plasma
systems, such as a capacitive system. The high density plasma
etchers dissociate gases so well that by providing oxygen to the
chamber the chamber walls are cleaned. This cleaning may be caused
by the heat generated by the plasma, UV radiation generated by the
plasma, and a lot of dissociation caused by the plasma.
[0003] Medium density plasma etching systems, such as capacitive
plasma systems, may be used for oxide etching. In such medium
density plasma etching systems a polymer forming chemistry is
typically employed. Such medium density plasma etching systems
typically cause polymer deposits to form on the chamber wall. Such
systems usually allow the polymer deposits to build on the chamber
walls and then are wet cleaned to remove the polymer deposits. The
wet cleaning is typically required in medium density plasma
systems, since such systems typically do not have sufficient
dissociation, and sufficient plasma energy contacting the walls to
perform a satisfactory polymer cleaning. When the chamber walls are
only partially cleaned and polymer is not satisfactorily removed,
sometimes new polymer does not sufficiently stick to the chamber
wall possibly creating particles, which could be an added source of
contamination. Plasma etching systems that use plasma confinement,
such as the device disclosed in U.S. Pat. No. 5,534,751 by Lenz et
al., entitled "Plasma Etching Apparatus Utilizing Plasma
Confinement", issued Jul. 9, 1996, generally confine a plasma
within a confinement ring that keeps the plasma in a confined area
away from the chamber wall. Keeping the plasma in a confined area
generally provides a dense enough and hot enough plasma adjacent to
the confinement ring to clean the confinement ring.
[0004] It is known to provide CVD devices with remote plasma
sources, which are typically used to clean the CVD chamber.
Typically such plasma devices use a fluorine chemistry. Such CVD
devices are used for vapor deposition.
[0005] It is known to use a remote plasma source in a strip
chamber, which typically uses the remotely generated plasma to
strip an etch mask.
[0006] In view of the foregoing, it would be desirable in medium
density plasma systems, where a plasma of a density that is
insufficient to sufficiently clean the chamber wall is generated by
the medium density plasma systems, to provide a means for providing
a plasma to sufficiently clean the chamber walls.
SUMMARY OF THE INVENTION
[0007] The invention relates, in one embodiment, to a medium
density dielectric plasma etching system with an additional remote
plasma source to provide a cleaning of the plasma system and to
possibly allow stripping within the etching system.
[0008] The invention relates, in a second embodiment, to a medium
density plasma system with an additional remote plasma source and
with a heater for heating the walls of the chamber to allow
cleaning of the chamber wall.
[0009] The invention relates, in a third embodiment, to a confined
medium density plasma system with an additional remote plasma
source to increase the rate of in situ stripping.
[0010] These and other features of the present invention will be
described in more detail below in the detailed description of the
invention and in conjunction with the following figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] 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:
[0012] FIG. 1 is a schematic view of an etch chamber.
[0013] FIG. 2 is a flow chart of the process for using the etch
chamber shown in FIG. 1.
[0014] FIG. 3 is a schematic view of another etch chamber.
[0015] FIG. 4 is a flow chart of the process for using the etch
chamber shown in FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] The present invention will now be described in detail with
reference to a few preferred embodiments thereof as illustrated in
the accompanying drawings.
[0017] In the following description, numerous specific details are
set forth in order to provide a thorough understanding of the
present invention. It will be apparent, however, to one skilled in
the art, that the present invention may be practiced without some
or all of these specific details. In other instances, well-known
process steps and/or structures have not been described in detail
in order to not unnecessarily obscure the present invention. To
facilitate discussion, FIG. 1 depicts a schematic view of an etch
chamber 10 of a preferred embodiment of the invention. The etch
chamber 10 comprises a chamber wall 12 which is grounded, an
electrostatic chuck 14 connected to a radio frequency energy source
16, an etchant gas distribution system 18 at the top of the etch
chamber 10 connected to an etchant gas source 20, heaters 22
adjacent to and surrounding the chamber wall 12, and a remote
plasma source 24 connected to a stripping gas source 25. The
chamber wall 12 may be of anodized aluminum or a conductive
ceramic.
[0018] FIG. 2 is a flow chart of the operation of the etch chamber
used in a preferred embodiment of the invention. A wafer 26 is
mounted on the electrostatic chuck 14 within and near the bottom of
the etch chamber 10 (step 201). The wafer 26 has a dielectric layer
28, such as an oxide layer of silicon oxide or a nitride layer,
where part of the dielectric layer 28 is covered by a resist mask
30 and part of the dielectric layer 28 is not covered by the resist
mask 30.
[0019] Next the etch chamber 10 etches away the part of the
dielectric layer 28 that is not covered by the resist mask 30 (step
202). This is accomplished by flowing an etchant gas into the etch
chamber 10, so that the pressure in the etch chamber is between 20
and 200 milliTorr. In the preferred embodiment of the invention the
etchant gas comprises a fluorocarbon gas with a generic molecular
formula of C.sub.YF.sub.X and oxygen. The amount of the etchant gas
used is known in the prior art. The etchant gas is provided by the
etchant gas source 20 through the etchant gas distribution system
18 at the top of the etch chamber 10. The radio frequency energy
source 16 provides a radio frequency signal to the electrostatic
chuck 14, which creates radio frequency waves between the
electrostatic chuck 14 and the grounded chamber wall 12, which
energizes the etchant gas with the electrostatic chuck 14 acting as
a cathode and the chamber wall 12 acting as an anode. The energized
etchant gas dissociates into ions, which are energized by the radio
frequency wave, creating a plasma within the chamber and
surrounding the wafer 26. Since the wafer is within the plasma, the
parts of the dielectric layer 28 that are not covered by the resist
mask 30 are etched away. Since the chamber wall 12, electrostatic
chuck 14, energy source 16, etchant gas distribution system 18, and
etchant gas source 20 form and sustain the plasma around the wafer,
these components provide an in situ plasma. As a result of the
etching process, a polymer residue 32, formed from the resist mask
30 and fluorocarbon etchant gas, forms on the chamber wall 12. When
the dielectric layer 28 is sufficiently etched the etching step
(step 202) is stopped by stopping the generation of the in situ
plasma.
[0020] The remote plasma source 24 is shown connected to the
chamber wall 12. The remote plasma source 24 may be placed at
another location around the etch chamber 10. The entry between the
remote plasma source 24 and the interior of the chamber 10 must be
sufficiently large so that a sufficient number of oxygen radicals
created in the remote plasma source 24 are able to pass from the
remote plasma source 24 to the interior of the chamber 10 without
being lost. The remote plasma source 24 may use either a microwave
or an inductive discharge or some other high density dissociative
remote source. An example of such a remote source is an ASTRON by
ASTeX of Woburn, Mass. Oxygen is provided to the remote plasma
source 24 from the stripping gas source 25. The remote plasma
source 24 dissociates the oxygen creating oxygen radicals, which
are flowed into the etch chamber 10, so that the pressure in the
chamber is between 100 and 1,000 milliTorr. The oxygen radicals
react with the resist mask 30 to strip away the resist mask 30
(step 204). In the preferred embodiment, the flow of the etch gas
from the etch gas source 20 and power from the radio frequency
energy source 16 is discontinued, so that the stripping of the
resist mask 30 is accomplished solely by the oxygen radicals. In
another embodiment, the in situ plasma may be used in combination
with the remote plasma to provide stripping. In another embodiment,
for the stripping gas, a hydrogen and nitrogen mixture may be used
separately or in combination with oxygen.
[0021] To discontinue the stripping step, the flow of the reactants
from the remote plasma source 24 is stopped. The wafer 26 is
removed from the etch chamber 10 (step 206). To clean the polymer
residue 32 from the chamber wall 12 the chamber wall heater 22
heats the chamber wall 12. In a preferred embodiment, the chamber
wall is heated to a temperature of 80.degree. to 300.degree. C. In
a more preferred embodiment of the invention, the chamber wall is
heated to a temperature of 120.degree. C. to 200.degree. C. In a
most preferred embodiment of the invention, the chamber wall is
heated to a temperature of 150.degree. C. Oxygen is provided to the
remote plasma source 24 from the stripping gas source 25. The
remote plasma source 24 dissociates the oxygen creating oxygen
radicals, which are flowed into the etch chamber 10, so that the
pressure in the chamber is between 100 and 1,000 milliTorr. The
oxygen radicals react with the heated chamber wall 12 to clean the
polymer residue 32 from the chamber wall 12 (step 208). In another
embodiment a hydrogen and nitrogen mixture may be used separately
or in combination with oxygen as a plasma source from the remote
plasma source. When the chamber wall 12 is sufficiently clean, the
plasma from the remote plasma source 24 is stopped and the etch
chamber 10 is ready for the next wafer.
[0022] FIG. 3 is a schematic view of an etch chamber 40 of another
preferred embodiment of the invention that uses a confined plasma.
The etch chamber 40 comprises a chamber wall 42, an electrostatic
chuck 44 connected to a radio frequency (RF) energy source 46, an
anode 48 that is grounded, an etchant gas source 50, confinement
rings 52 and a remote plasma source 54 connected to a stripping gas
source 55. The electrostatic chuck 44 which acts as a cathode at
the bottom of the etch chamber 40 and the anode 48 at the top of
the etch chamber 40 are placed close together to confine the plasma
region to a small area. The confinement rings 52 surround the sides
of the plasma region to further confine the plasma region, keeping
the plasma near the center of the etch chamber 40 and away from the
chamber wall 42. The confinement rings 52 may be made of quartz and
are formed as ring shaped plates that are spaced apart with narrow
gaps between the confinement rings 52. In this example, three
confinement rings 52 are shown, but one or more confinement rings
may be used in other embodiments. The narrow gaps between the
confinement rings 52 keep the plasma from reaching the chamber wall
42, since the gaps are so small that most plasma passing within the
gap will be extinguished by a collision with a confinement ring 52
before the plasma reaches the chamber wall 42.
[0023] FIG. 4 is a flow chart of the operation of the etch chamber
used in a preferred embodiment of the invention. A wafer 56 is
mounted on the electrostatic chuck 44 within and near the bottom of
the etch chamber 40 (step 401). The wafer 56 has a dielectric layer
58, such as an oxide layer of silicon oxide or a nitride layer,
where part of the dielectric layer 58 is covered by a resist mask
60 and part of the dielectric layer 58 is not covered by the resist
mask 60.
[0024] Next the etch chamber 40 etches away the part of the
dielectric layer 58 that is not covered by the resist mask 60 (step
402). This is accomplished by flowing an etchant gas into the etch
chamber 40, so that the pressure in the etch chamber is between 20
and 200 milliTorr. In the preferred embodiment of the invention,
the etchant gas comprises a fluorocarbon gas with a generic
molecular formula of C.sub.YF.sub.X and oxygen. The amount of the
etchant gas used is known in the prior art. The etchant gas is
provided by the etchant gas source 50 connected to the etch chamber
40. The radio frequency energy source 46 provides a radio frequency
signal to the electrostatic chuck 44, which creates radio frequency
waves between the electrostatic chuck 44 and the grounded anode 48,
which energizes the etchant gas. The energized etchant gas
dissociates into ions, which are energized by the radio frequency
wave, creating a plasma within the chamber and surrounding the
wafer 56. Since the wafer is within the plasma, the parts of the
dielectric layer 58 that are not covered by the resist mask 60 are
etched away. Since the electrostatic chuck 44, energy source 46,
anode 48, and etchant gas source 50 form and sustain the plasma
around the wafer, these components provide an in situ plasma. As a
result of the etching process, a polymer residue 62, formed from
the resist mask 60 and fluorocarbon etchant gas, forms on the
confinement rings 52. When the dielectric layer 58 is sufficiently
etched, the etching step (step 402) is stopped by stopping the
generation of the in situ plasma.
[0025] The remote plasma source 54 is shown connected to the etch
chamber wall 40 through the anode 48. The entry between the remote
plasma source 54 and the interior of the chamber 40 must be
sufficiently large so that a sufficient number of oxygen radicals
created in the remote plasma source 54 are able to pass from the
remote plasma source 54 to the interior of the chamber 40 without
being lost. The remote plasma source 54 may use either a microwave
or an inductive discharge or some other high density dissociative
remote source. An example of such a remote source is an ASTRON by
ASTeX of Woburn, Massachusetts. Oxygen is provided to the remote
plasma source 54 from the stripping gas source 55. The remote
plasma source 54 dissociates the oxygen creating oxygen radicals,
which are flowed into the etch chamber 40, so that the pressure in
the chamber is between 100 and 1,000 milliTorr. The oxygen radicals
react with the resist mask 60 to strip away the resist mask 60
(step 404). In the preferred embodiment, the flow of the etch gas
from the etch gas source 50 and power from the radio frequency
energy source 46 is continued, so that the stripping of the resist
mask 60 is accomplished by the oxygen radicals from the remote
plasma source 54 and in situ plasma. In another embodiment, a
hydrogen and nitrogen mixture may be used separately or in
combination with oxygen as a plasma source from the remote plasma
source. To discontinue the stripping step, the flow of the
reactants from the remote plasma source 54 and the in situ plasma
are stopped.
[0026] The wafer 56 is removed from the etch chamber 40 (step 406).
To clean the polymer residue 62 from the confinement rings 52, an
oxygen or nitrogen/hydrogen etchant gas is flowed into the etch
chamber 40 so that the pressure in the chamber is between 100 and
1,000 milliTorr. The amount of the etchant gas used is known in the
prior art. The radio frequency energy source 46 provides a radio
frequency signal to the electrostatic chuck 44, which creates radio
frequency waves between the electrostatic chuck 44 and the grounded
anode 48, which energizes the etchant gas. The energized etchant
gas dissociates into ions, which are energized by the radio
frequency wave, creating a plasma within the chamber and
surrounding the wafer 56. Since the in situ plasma is confined to a
small region by the electrostatic chuck 44, the anode 48, and the
confinement rings 52, the in situ plasma is dense and energetic
enough to clean the polymer residue 62 from the confinement rings
52. When the confinement rings 52 are sufficiently clean, the in
situ plasma is stopped and the etch chamber 40 is ready for the
next wafer.
[0027] In another embodiment, the in situ plasma and the remote
plasma are both used for cleaning either in an etch chamber without
a confined plasma or an etch chamber with a confined plasma.
[0028] While this invention has been described in terms of several
preferred embodiments, there are alterations, permutations, and
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
equivalents as fall within the true spirit and scope of the present
invention.
* * * * *