U.S. patent application number 10/410803 was filed with the patent office on 2004-01-22 for method for etching high dielectric constant materials and for cleaning deposition chambers for high dielectric constant materials.
Invention is credited to Ji, Bing, Karwacki, Eugene Joseph JR., Motika, Stephen Andrew, Pearlstein, Ronald Martin, Wu, Dingjun.
Application Number | 20040011380 10/410803 |
Document ID | / |
Family ID | 46299158 |
Filed Date | 2004-01-22 |
United States Patent
Application |
20040011380 |
Kind Code |
A1 |
Ji, Bing ; et al. |
January 22, 2004 |
Method for etching high dielectric constant materials and for
cleaning deposition chambers for high dielectric constant
materials
Abstract
A process for the removal of a substance from a substrate for
etching and/or cleaning applications is disclosed herein. In one
embodiment, there is provided a process for removing a substance
having a dielectric constant greater than silicon dioxide from a
substrate by reacting the substance with a reactive agent that
comprises at least one member from the group consisting a
halogen-containing compound, a boron-containing compound, a
hydrogen-containing compound, nitrogen-containing compound, a
chelating compound, a carbon-containing compound, a chlorosilane, a
hydrochlorosilane, or an organochlorosilane to form a volatile
product and removing the volatile product from the substrate to
thereby remove the substance from the substrate.
Inventors: |
Ji, Bing; (Allentown,
PA) ; Motika, Stephen Andrew; (Kutztown, PA) ;
Pearlstein, Ronald Martin; (Macungie, PA) ; Karwacki,
Eugene Joseph JR.; (Orefield, PA) ; Wu, Dingjun;
(Macungie, PA) |
Correspondence
Address: |
AIR PRODUCTS AND CHEMICALS, INC.
PATENT DEPARTMENT
7201 HAMILTON BOULEVARD
ALLENTOWN
PA
181951501
|
Family ID: |
46299158 |
Appl. No.: |
10/410803 |
Filed: |
April 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10410803 |
Apr 10, 2003 |
|
|
|
10198509 |
Jul 18, 2002 |
|
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Current U.S.
Class: |
134/1.1 ;
134/166R; 134/22.1; 134/30 |
Current CPC
Class: |
B08B 7/0035 20130101;
B08B 7/00 20130101; C23C 16/4405 20130101 |
Class at
Publication: |
134/1.1 ;
134/22.1; 134/30; 134/166.00R |
International
Class: |
C25F 001/00 |
Claims
1. A process for cleaning a substance from a reactor surface, said
process comprising: providing a reactor containing the reactor
surface, wherein: (a) the reactor surface is at least partially
coated with a film of the substance; (b) the substance is at least
one member selected from the group consisting of a transition metal
oxide, a transition metal silicate, a Group 13 metal oxide, a Group
13 metal silicate, a nitrogen containing Group 13 metal oxide, a
nitrogen containing Group 13 metal silicate, a nitrogen containing
transition metal oxide, a nitrogen containing transition metal
silicate, or a laminate comprising at least one layer selected from
the group consisting of a transition metal oxide, a transition
metal silicate, a Group 13 metal oxide, a Group 13 metal silicate,
a nitrogen containing transition metal oxide, a nitrogen containing
transition metal silicate, a nitrogen containing Group 13 metal
oxide, or a nitrogen containing Group 13 metal silicate; and (c)
the substance has a dielectric constant greater than the dielectric
constant of silicon dioxide; reacting the substance with a reactive
agent to form a volatile product, wherein the reactive agent
comprises at least one member selected from the group consisting of
a halogen-containing compound; a boron-containing compound, a
carbon-containing compound, a hydrogen-containing compound, a
nitrogen-containing compound, a chelating compound, a chlorosilane
compound, a hydrochlorosilane compound, or an organochlorosilane
compound; and removing the volatile product from the reactor to
thereby remove the substance from the surface.
2. The process of claim 1, wherein the reactor is an atomic layer
deposition reactor.
3. The process of claim 1, wherein the substance is at least one
member selected from the group consisting of Al.sub.2O.sub.3,
HfO.sub.2, ZrO.sub.2, HfSi.sub.xO.sub.y, and ZrSi.sub.xO.sub.y
wherein x is a number greater than 0 and y is 2x +2, and any of the
aforementioned compounds containing nitrogen.
4. The process of claim 1 wherein the reactive agent is at least
one member selected from the group consisting of BCl.sub.3,
COCl.sub.2, HCl, Cl.sub.2, ClF.sub.3, and NF.sub.zCl.sub.3-z, where
z is an integer from 0 to 2.
5. The process of claim 4, wherein the reactive agent is COCl.sub.2
formed by an in situ reaction of CO and Cl.sub.2.
6. The process of claim 4, wherein the reactive agent is
BCl.sub.3.
7. The process of claim 1 wherein the reactive agent is a
carbon-containing compound having the formula
C.sub.xH.sub.yCl.sub.z, wherein x is a number ranging from 1 to 6,
y is a number ranging from 0 to 13, and z is a number ranging 1
from 14.
8. The process of claim 1, wherein the reactive agent is conveyed
to the substance from a gas cylinder, a safe delivery system or a
vacuum delivery system.
9. The process of claim 1, wherein the reactive agent is formed in
situ by a point-of-use generator.
10. The process of claim 1, wherein the substance is contacted with
the reactive agent diluted with an inert gas diluent.
11. A process for removing a substance from at least a portion of
the surface of a reaction chamber, the process comprising:
providing a reaction chamber wherein at least a portion of the
surface is at least partially coated with the substance and wherein
the substance has a dielectric constant of 4.1 or greater and is at
least one member of the group consisting of a transition metal
oxide, a transition metal silicate, a Group 13 metal oxide, a Group
13 metal silicate, a nitrogen containing Group 13 metal oxide, a
nitrogen containing Group 13 metal silicate, a nitrogen containing
transition metal oxide, a nitrogen containing transition metal
silicate, or a laminate comprising at least one layer of the group
consisting of a transition metal oxide, a transition metal
silicate, a Group 13 metal oxide, a Group 13 metal silicate, a
nitrogen containing Group 13 metal oxide, a nitrogen containing
Group 13 metal silicate, a nitrogen containing transition metal
oxide, a nitrogen containing transition metal silicate; introducing
a reactive agent into the reaction chamber wherein the reactive
agent comprises at least one member selected from the group
consisting of a halogen-containing compound; a boron-containing
compound, a carbon-containing compound, a hydrogen-containing
compound, a nitrogen-containing compound, a chelating compound, a
chlorosilane compound, a hydrochlorosilane compound, or an
organochlorosilane compound; exposing the reactive agent to one or
more energy sources sufficient to react the substance with the
reactive agent and form a volatile product; and removing the
volatile product from the reaction chamber.
12. The process of claim 11, wherein the reactive agent is conveyed
to the substance from a gas cylinder, a safe delivery system or a
vacuum delivery system.
13. The process of claim 11, wherein the reactive agent is formed
in situ by a point-of-use generator.
14. The process of claim 11, wherein the substance is contacted
with the reactive agent diluted with an inert gas diluent.
15. The process of claim 11 wherein the reactive agent is deposited
onto a nonreactive support.
16. The process of claim 11 wherein the reactive agent is exposed
to one or more energy sources and the exposing step is conducted
prior to the introducing step.
17. The process of claim 11 wherein the reactive agent is exposed
to one or more energy sources and the exposing step is conducted
during at least a portion of the introducing step.
18. The process of claim 11 wherein a temperature of the exposing
step is at least 150.degree. C.
19. The process of claim 11 wherein a pressure of the exposing step
is at least 10 mTorr.
20. An apparatus for removing a substance from at least one surface
of a reactor, the apparatus comprising: an at least one reactive
agent selected from the group consisting of a halogen-containing
compound; a boron-containing compound, a carbon-containing
compound, a hydrogen-containing compound, a nitrogen-containing
compound, a chelating compound, a chlorosilane compound, a
hydrochlorosilane compound, or an organochlorosilane compound; and
a non-reactive support having the at least one reactive agent
deposited thereupon.
21. A mixture for removing a substance from at least one surface of
a reactor, the mixture comprising: an at least one reactive agent
selected from the group consisting of a halogen-containing
compound; a boron-containing compound, a carbon-containing
compound, a hydrogen-containing compound, a nitrogen-containing
compound, a chelating compound, a chlorosilane compound, a
hydrochlorosilane compound, or an organochlorosilane compound; and
an inert diluent.
22. A process for removing a substance from an at least one surface
of a substrate, said process comprising: providing the substrate
wherein the substrate is at least partially coated with a film of
the substance that is at least one member selected from the group
consisting of a transition metal oxide, a transition metal
silicate, a Group 13 metal oxide other than Al.sub.2O.sub.3, a
Group 13 metal silicate, a nitrogen containing Group 13 metal
oxide, a nitrogen containing Group 13 metal silicate, a nitrogen
containing transition metal oxide, a nitrogen containing transition
metal silicate, or a laminate comprising at least one layer of the
group consisting of a transition metal oxide, a transition metal
silicate, a Group 13 metal oxide, a Group 13 metal silicate, a
nitrogen containing Group 13 metal oxide, a nitrogen containing
Group 13 metal silicate, a nitrogen containing transition metal
oxide, or a nitrogen containing transition metal silicate; and
wherein the substance has a dielectric constant greater than a
dielectric constant of silicon dioxide; reacting the substance with
a reactive agent to form a volatile product, wherein the reactive
agent comprises at least one member from the group consisting of a
halogen-containing compound ; a boron-containing compound, a
carbon-containing compound, a hydrogen-containing compound, a
nitrogen-containing compound, a chelating compound, a chlorosilane
compound, a hydrochlorosilane compound, or an organochlorosilane
compound; and removing the volatile product from the substrate to
thereby remove the substance from the substrate.
23. The process of claim 22, wherein the substance is at least one
member selected from the group consisting of HfO.sub.2, ZrO.sub.2,
HfSi.sub.xO.sub.y, ZrSi.sub.xO.sub.y where x is greater than 0 and
y is 2x +2, Al.sub.2Si.sub.wO.sub.z, where w is greater than 0 and
z is 2w +3, or any of the aforementioned compounds containing
nitrogen.
24. The process of claim 22, wherein the substance is a laminate
comprising layers of at least one material selected from the group
consisting of a transition metal oxide, a transition metal
silicate, a Group 13 metal oxide, a Group 13 metal silicate, a
nitrogen containing transition metal oxide, a nitrogen containing
transition metal silicate, a nitrogen containing Group 13 metal
oxide, or a nitrogen containing Group 13 metal silicate.
25. The process of claim 22, wherein the reactive agent is at least
one member selected from the group consisting of BCl.sub.3,
COCl.sub.2, HCl, Cl.sub.2, ClF.sub.3, and NF.sub.zCl.sub.3-z, where
z is an integer from 0 to 2.
26. The process of claim 25, wherein the substance is at least one
member selected from the group consisting of HfO.sub.2, ZrO.sub.2,
HfSi.sub.xO.sub.y, ZrSi.sub.xO.sub.y, where x is greater than 0 and
y is 2x +2, Al.sub.2Si.sub.wO.sub.z, where w is greater than 0 and
z is 2w +3, or any of the aforementioned compounds containing
nitrogen.
27. The process of claim 25, wherein the reactive agent is
COCl.sub.2 formed by an in situ reaction of CO and Cl.sub.2.
28. The process of claim 25, wherein the reactive agent is
BCl.sub.3.
29. The process of claim 22 wherein the reactive agent is a
carbon-containing compound having the formula
C.sub.xH.sub.yCl.sub.z, wherein x is a number ranging from 1 to 6,
y is a number ranging from 0 to 13, and z is a number ranging 1
from 14.
30. The process of claim 22 wherein the reactive agent is conveyed
to the substance from a gas cylinder, a safe delivery system or a
vacuum delivery system.
31. The process of claim 22 wherein the reactive agent is formed in
situ by a point-of-use generator.
32. The process of claim 22 wherein the substance is contacted with
the reactive agent diluted with an inert gas diluent.
33. The process of claim 22, wherein the substance is coated on the
substrate by atomic layer deposition.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 10/198,509, filed Jul. 18, 2002, the
disclosure of which is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a method to etch high-k dielectric
materials deposited on a substrate, and a method to clean residues
from the internal surfaces of a reactor in which these high-k
dielectric films are deposited.
[0003] In the manufacture of semiconductor integrated circuits
(IC), dielectric materials such as silicon dioxide (SiO.sub.2),
silicon nitride (Si.sub.3N.sub.4), and silicon oxynitride (SiON)
have been widely used as insulators for transistor gates. Such
insulators are often called gate dielectrics. As IC device geometry
shrinks, gate dielectric layers have become progressively thinner.
When the gate dielectric layer approaches thicknesses of a few
nanometers or less, conventional SiO.sub.2, Si.sub.3N.sub.4, and
SiON materials undergo electric breakdown and no longer provide
insulation. To maintain adequate breakdown voltage at very small
thickness (.ltoreq.10 nm), high dielectric constant materials
(i.e., high-k materials, which for present purposes are defined as
materials where k is greater than about 4.1, the k of silicon
dioxide) can be used as the gate insulating layer. In addition,
high-k materials can also be used as the barrier layer in deep
trench capacitors for semiconductor memory chip manufacturing. The
IC industry has experimented with many high-k materials. The latest
and most promising high-k materials are metal oxides such as
Al.sub.2O.sub.3, HfO.sub.2, ZrO.sub.2, and mixtures thereof, and
metal silicates such as HfSi.sub.xO.sub.y, ZrSiO.sub.4, and
mixtures thereof. In some instances, nitrogen may be incorporated
into these metal oxides and metal silicates high-k materials (such
as HfSiON or AlSiON) to improve the dielectric constant and to
suppress crystallization of high-k materials. Crystallization of
high-k materials such as HfO.sub.2 causes high leakage current and
device failure. Therefore, incorporation of nitrogen can
dramatically improve the device reliability.
[0004] High-k materials such as Al.sub.2O.sub.3, HfO.sub.2, and
ZrO.sub.2 are very stable and resistive against most of the etching
reactions, which has led to their use as etch stop layers and hard
mask layers in plasma etching of other materials. See, e.g., K. K.
Shih et al., "Hafnium dioxide etch-stop layer for phase-shifting
masks", J. Vac. Sci. Technol. B 11(6), pp. 2130-2131 (1993); J. A.
Britten, et al., "Etch-stop characteristics of Sc.sub.2O.sub.3 and
HfO.sub.2 films for multilayer dielectric grating applications", J.
Vac. Sci. Technol. A 14(5), pp. 2973-2975 (1996); J. Hong et al.,
"Comparison of Cl.sub.2 and F.sub.2 based chemistries for the
inductively coupled plasma etching of NiMnSb thin films", J. Vac.
Sci. Technol. A 17(4), pp. 1326-1330 (1999); U.S. Pat. No.
5,972,722 to Visokay et al.; U.S. Pat. No. 6,211,035 B1 to Moise et
al., U.S. patent application Publication US2001/0055852 A1 to Moise
et al.; and EP 1,001,459 A2 to Moise et al.
[0005] These high-k materials are typically deposited from chemical
precursors that react in a deposition chamber to form films in a
chemical vapor deposition (CVD) process. In some instances, these
high-k materials are deposited onto semiconductor substrates
(wafers) by atomic layer deposition (ALD), in which the films are
deposited in controlled, nearly monoatomic layers. Apparatus and
processes for performing ALD are disclosed in, e.g., U.S. Pat. No.
5,879,459 to Gadgil et al., U.S. Pat. No. 6,174,377 B1 to Doering
et al., U.S. patent application Publication US2001/0011526 A1 to
Doering et al., U.S. Pat. No. 6,387,185 B2 to Doering et al., WO
00/40772 to Doering et al. and WO 00/79019 A1 to Gadgil et al. This
family of patents assigned to Genus, Inc. teaches that "In situ
plasma cleans allow the realization of a very long time between
maintenance cleaning." (See, e.g., U.S. Pat. No. 6,387,185 B2 at
column 7, lines 27-28.) However, no details of any process for
plasma cleaning of ALD chambers were given in the above family of
disclosures.
[0006] Plasma sources have been used to enhance atomic layer
deposition processes (PE-ALD). For example, Pomarede et al. in WO
02/43115 A2 teach the use of plasma sources to generate excited
reactive species that prepare/activate the substrate surface to
facilitate subsequent ALD. Nguyen et al. in WO 02/43114 A2 teach
the use of a pulsing plasma to enact ALD processes instead of
alternating precursor chemical flows. Again, these publications do
not disclose any method to clean the ALD residues after the wafers
have been processed.
[0007] Although the aforementioned high-k materials are excellent
gate insulators, it is very difficult to dry etch these films for
pattern transfer. While the deposition process desirably generates
high-k films on a substrate (typically a silicon wafer), the
reactions that form these films also occur non-productively on
other exposed surfaces inside of the deposition chamber.
Accumulation of deposition residues results in particle shedding,
degradation of deposition uniformity, and processing drifts. These
effects can lead to wafer defects and subsequent device failure.
Therefore, all CVD chambers, and specifically ALD chambers, must be
periodically cleaned.
[0008] Due to their extreme chemical inertness, there have been few
attempts to dry etch these high-k materials. J. W. Lee et al. in
"Electron cyclotron resonance plasma etching of oxides and SrS and
ZnS-based electroluminescent materials for flat panel displays", J.
Vac. Sci. Technol. A 16(3), pp. 1944-1948 (1998), reported several
chemistries to etch various metal oxides and sulfides. The authors
used very powerful plasma conditions (800 W of microwave source
power, up to 450 W of RF chuck bias power, and chamber pressure of
1.5 mTorr). The result of such process conditions is very high
chuck bias voltage (up to 535 V). High chuck bias voltage can
greatly enhance energetic ion sputtering and sputter induced
etching. The authors used Cl.sub.2/Ar, BCl.sub.3/Ar, and
SF.sub.6/Ar mixture under the extreme plasma conditions to etch
various materials. Al.sub.2O.sub.3 showed the slowest etch rates.
In most of their experiments, Al.sub.2O.sub.3 etch rates were less
than 20% of the ZnS etch rates under identical conditions. The
authors also noted "Fairly similar trends were seen with
BCl.sub.3/Ar discharges, with the absolute rates being .about.20%
lower than that for Cl.sub.2/Ar." While the authors' method may be
used for anisotropic etching of flat panel display devices, high
power plasma sputtering cannot be achieved on grounded chamber
surfaces. Therefore, the authors' methods cannot be extended to
clean deposition residues within ALD chambers.
[0009] Williams et al. in U.S. Pat. No. 6,238,582 B1 teach a
reactive ion beam etching (RIBE) method to etch thin film head
materials such as Al.sub.2O.sub.3. The patentees used a
CHF.sub.3/Ar plasma as the ion source. A collimated reactive ion
beam impinges upon the wafer substrate to etch thin film materials.
Such collimated ion beams cannot be used to clean deposition
residues from ALD chambers.
[0010] Lagendijk et al. in U.S. Pat. Nos. 5,298,075 and 5,288,662
teach a "process for thermal oxidation of silicon or cleaning of
furnace tubes . . . by exposing the silicon or tube to temperatures
above 700.degree. C. while flowing a carrier gas containing oxygen
and a chlorohydrocarbon having a general formula
C.sub.xH.sub.xCl.sub.x where x is 2, 3, or 4 over the silicon or
tube. The chlorohydrocarbon is selected to readily and completely
oxidize at temperature." (See Abstract.) Oxidation of silicon into
SiO.sub.2 and gettering metal contaminants (such as Na and Fe) in
oxidation or diffusion furnaces is a completely different process
than etching/cleaning high-k materials.
[0011] Various references discuss adding certain compounds to the
plasma in order to effect the etch rate of Al.sub.2O.sub.3. The
references, W. G. M. Van Den Hoek, "The Etch Mechanism for
Al.sub.2O.sub.3 in Fluorine and Chlorine Based RF Dry Etch
Plasmas". Met. Res. Soc. Symp. Proc. Vol. 68 (1986), pp. 71-78 and
Heiman, et al., "High Rate Reactive Ion Etching of Al.sub.2O.sub.3
and Si", J. Vac. Sci. Tech., 17(3), May/June 1980, pp. 731-34,
disclose adding a fluorine based gas or a chlorine based gas,
respectively, to an Ar plasma to increase the etch rate of
Al.sub.2O.sub.3. However, these studies were all under the reactive
ion etch (RIE) conditions. Ion bombardment/sputter induced
reactions play a much large role than chemical etching reactions.
Like other prior arts, such extreme RIE conditions do not apply to
cleaning grounded chamber surfaces.
[0012] In view of the dearth of art disclosing the removal of high
k dielectric residues, ALD reactors have typically been cleaned by
mechanical means (scrubbing or blasting) to clean up the deposition
residues from the internal surfaces of the chamber and downstream
equipment (e.g. pump headers and exhaust manifolds). However,
mechanical cleaning methods are time-consuming, labor-intensive,
and damaging to the surfaces being cleaned.
[0013] Fluorine-containing plasma-based processes (i.e., dry
cleaning) are commonly used to remove residues of silicon compounds
(such as polycrystalline silicon, SiO.sub.2, SiON, and
Si.sub.3N.sub.4) and tungsten from the interior surfaces of
chemical vapor deposition (CVD) reactors. Here, fluorine reacts
with the aforementioned residues to produce SiF.sub.4, a volatile
species that can be pumped out of the reactor during the cleaning
process. However, fluorine-based chemistry alone is ineffective to
remove the high-k dielectric materials discussed above. See, e.g.,
J. Hong et al., J. Vac. Sci. Technol. A, Vol. 17, pp1326-1330,
1999, wherein the authors exposed Al.sub.2O.sub.3 coated wafers to
NF.sub.3/Ar based inductively coupled plasmas, and found that "the
greater concentration of atomic F available at high source power
contributed to thicker fluorinated surfaces, leading to the net
deposition rather than etching." In the case of high-k materials
the metal fluoride product that forms is nonvolatile and, thus,
difficult to remove from the reactor.
[0014] Thus, there is an urgent need for a process to chemically
dry clean high-k material residues, such as Al.sub.2O.sub.3,
HfO.sub.2, ZrO.sub.2, HfSi.sub.xO.sub.y, ZrSi.sub.xO.sub.y and
mixtures thereof, residues of laminates containing high-k materials
such as HfAIO, and residues from nitrogen containing high-k
material such as HfAlON, from ALD chambers without venting/opening
up the chamber. An effective chemical dry cleaning method will
significantly increase the productivity and lower the
cost-of-ownership (CoO) for ALD-based deposition processes.
[0015] All references cited herein are incorporated herein by
reference in their entireties.
BRIEF SUMMARY OF THE INVENTION
[0016] Accordingly, the invention provides process for cleaning a
substance from a reactor surface comprising: providing a reactor
containing the reactor surface, wherein: (a) the reactor surface is
at least partially coated with a film of the substance; (b) the
substance is at least one member selected from the group consisting
of a transition metal oxide, a transition metal silicate, a Group
13 metal oxide, a Group 13 metal silicate, a nitrogen containing
Group 13 metal oxide, a nitrogen containing Group 13 metal
silicate, a nitrogen containing transition metal oxide, a nitrogen
containing transition metal silicate, or a laminate comprising at
least one layer selected from the group consisting of a transition
metal oxide, a transition metal silicate, a Group 13 metal oxide, a
Group 13 metal silicate, a nitrogen containing transition metal
oxide, a nitrogen containing transition metal silicate, a nitrogen
containing Group 13 metal oxide, or a nitrogen containing Group 13
metal silicate; and (c) the substance has a dielectric constant
greater than the dielectric constant of silicon dioxide; reacting
the substance with a reactive agent to form a volatile product,
wherein the reactive agent comprises at least one member selected
from the group consisting of a halogen-containing compound; a
boron-containing compound, a carbon-containing compound, a
hydrogen-containing compound, a nitrogen-containing compound, a
chelating compound, a chlorosilane compound, a hydrochlorosilane
compound, or an organochlorosilane compound; and removing the
volatile product from the reactor to thereby remove the substance
from the surface.
[0017] Further provided is a process for removing a substance from
a surface of a reaction chamber comprising: providing a reaction
chamber wherein at least a portion of the surface is at least
partially coated with the substance and wherein the substance has a
dielectric constant of 4.1 or greater and is at least one member of
the group consisting of a transition metal oxide, a transition
metal silicate, a Group 13 metal oxide, a Group 13 metal silicate,
a nitrogen containing Group 13 metal oxide, a nitrogen containing
Group 13 metal silicate, a nitrogen containing transition metal
oxide, a nitrogen containing transition metal silicate, or a
laminate comprising at least one layer of the group consisting of a
transition metal oxide, a transition metal silicate, a Group 13
metal oxide, a Group 13 metal silicate, a nitrogen containing Group
13 metal oxide, a nitrogen containing Group 13 metal silicate, a
nitrogen containing transition metal oxide, a nitrogen containing
transition metal silicate; introducing a reactive agent into the
reaction chamber wherein the reactive agent comprises at least one
member selected from the group consisting of a halogen-containing
compound; a boron-containing compound, a carbon-containing
compound, a hydrogen-containing compound, a nitrogen-containing
compound, a chelating compound, a chlorosilane compound, a
hydrochlorosilane compound, or an organochlorosilane compound;
exposing the reactive agent to one or more energy sources
sufficient to react the substance with the reactive agent and form
a volatile product; and removing the volatile product from the
reaction chamber.
[0018] Still further provided is an apparatus for removing a
substance from at least one surface of a reactor comprising: an at
least one reactive agent selected from the group consisting of a
halogen-containing compound; a boron-containing compound, a
carbon-containing compound, a hydrogen-containing compound, a
nitrogen-containing compound, a chelating compound, a chlorosilane
compound, a hydrochlorosilane compound, or an organochlorosilane
compound; and a non-reactive support having the at least one
reactive agent deposited thereupon.
[0019] Still also provided is a mixture for removing a substance
from at least one surface of a reactor comprising: an at least one
reactive agent selected from the group consisting of a
halogen-containing compound; a boron-containing compound, a
carbon-containing compound, a hydrogen-containing compound, a
nitrogen-containing compound, a chelating compound, a chlorosilane
compound, a hydrochlorosilane compound, or an organochlorosilane
compound; and an inert diluent.
[0020] Further provided is a process for removing a substance from
an at least one surface of a substrate comprising: providing the
substrate wherein the substrate is at least partially coated with a
film of the substance that is at least one member selected from the
group consisting of a transition metal oxide, a transition metal
silicate, a Group 13 metal oxide other than Al.sub.2O.sub.3, a
Group 13 metal silicate, a nitrogen containing Group 13 metal
oxide, a nitrogen containing Group 13 metal silicate, a nitrogen
containing transition metal oxide, a nitrogen containing transition
metal silicate, or a laminate comprising at least one layer of the
group consisting of a transition metal oxide, a transition metal
silicate, a Group 13 metal oxide, a Group 13 metal silicate, a
nitrogen containing Group 13 metal oxide, a nitrogen containing
Group 13 metal silicate, a nitrogen containing transition metal
oxide, or a nitrogen containing transition metal silicate; and
wherein the substance has a dielectric constant greater than a
dielectric constant of silicon dioxide; reacting the substance with
a reactive agent to form a volatile product, wherein the reactive
agent comprises at least one member from the group consisting of a
halogen-containing compound ; a boron-containing compound, a
carbon-containing compound, a hydrogen-containing compound, a
nitrogen-containing compound, a chelating compound, a chlorosilane
compound, a hydrochlorosilane compound, or an organochlorosilane
compound; and removing the volatile product from the substrate to
thereby remove the substance from the substrate.
[0021] These and other aspects of the invention will become
apparent from the following detailed description.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0022] FIGS. 1a and 1b provides an illustration of an apparatus
suitable for performing chamber cleaning using an internal energy
source or a remote energy source, respectively.
[0023] FIG. 2 provides an illustration of an apparatus for
performing a process of the invention using plasma as the energy
source.
[0024] FIG. 3 provides a graphical illustration of the relative
BCl.sub.3 plasma etch rates of various high dielectric constant
materials, normalized to Al.sub.2O.sub.3.
[0025] FIG. 4 provides an illustration of an apparatus for
performing a process of the invention using thermal heating as the
energy source
[0026] FIG. 5 provides an illustration of the etch rate dependence
on lower electrode/pedestal set temperature at constant chamber
pressure and BCl.sub.3 flow rate.
[0027] FIG. 6 provides an illustration of the etch rate dependence
on chamber pressure at constant lower electrode set temperature and
BCl.sub.3 flow rate.
DETAILED DESCRIPTION OF THE INVENTION
[0028] The inventive process is useful for dry-etching high-k
materials and dry-cleaning chemical vapor deposition (CVD) chambers
(and more specifically, ALD chambers) used to deposit high-k
materials onto wafer surfaces. The material to be removed from the
surface being etched or cleaned is converted from a solid
non-volatile material into species that have higher volatility than
the high-k materials deposited thereupon and can be subsequently
removed, for example, by reactor vacuum pumps. Thus, in preferred
embodiments, the invention removes a substance from a substrate
using a reactive agent to volatilize the substance. Unlike
wet-etching and wet-cleaning processes, dry-etching and
dry-cleaning processes do not immerse the substrate in or expose
the substrate to liquid chemical solutions.
[0029] In certain embodiments, the substance to be removed can be a
transition metal oxide, a transition metal silicate, a Group 13
metal oxide or a Group 13 metal silicate (in accordance with the
IUPAC Nomenclature of Inorganic Chemistry, Recommendations 1990,
Group 13 metals include Al, Ga, In and Tl, and the transition
metals occupy Groups 3-12). The substance may be a high-k material
having a dielectric constant greater than that of silicon dioxide
(i.e., greater than about 4.1), more preferably greater than 5,
even more preferably at least 7. Preferably, the substance is at
least one member selected from the group consisting of
Al.sub.2O.sub.3, HfO.sub.2, ZrO.sub.2, HfSi.sub.xO.sub.y,
ZrSi.sub.xO.sub.y, and mixtures thereof. Those skilled in the art
will appreciate that the formula HfSi.sub.xO.sub.y (and the formula
ZrSi.sub.xO.sub.y) represents a mixture of HfO.sub.2 (ZrO.sub.2)
and SiO.sub.2, where x is greater than 0 and y is2x+2.
[0030] In other embodiments of the present invention, the substance
may be a laminate comprising layers of at least one member selected
from the group of the following materials: a transition metal
oxide, a transition metal silicate, a Group 13 metal oxide, a Group
13 metal silicate, a nitrogen containing transition metal oxide, a
nitrogen containing transition metal silicate, a nitrogen
containing Group 13 metal oxide, or a nitrogen containing Group 13
metal silicate. The laminate is preferably alternating between at
least one of the foregoing materials and, optionally, other
materials such as insulating materials. For example, the laminate
may be comprised of alternating layers of HfO.sub.2 and
Al.sub.2O.sub.3. The laminate may also consist of a certain number
of layers of a first material and a certain number of layers of a
second material or, alternatively, outer layers of at least one
first material and inner layers of at least one second
material.
[0031] In yet a further embodiment of the present invention, the
substance may be a nitrogen containing material such as a nitrogen
containing transition metal oxide, a nitrogen containing transition
metal silicate, a nitrogen containing Group 13 metal oxide, or a
nitrogen containing Group 13 metal silicate. An example of this
type of substance includes HfAlON.
[0032] As mentioned previously, the substance to be removed is
reacted with a reactive agent to form a volatile product which can
be readily removed from the substrate. In certain preferred
embodiments, the reactive agent may be exposed to one or more
energy sources sufficient to form active species which react and
form the volatile product. Examples of suitable reactive agents
include: a halogen-containing compound such as a chloride, bromide,
or iodide compound; a boron-containing compound, a
carbon-containing compound, a hydrogen-containing compound, a
nitrogen-containing compound, a chelating compound, a chlorosilane
compound, a hydrochlorosilane compound, an organochlorosilane
compound, or a mixture thereof. Although the reactive agents used
herein may be sometimes described as "gaseous", it is understood
that the chemical reagents may be delivered directly as a gas to
the reactor, delivered as a vaporized liquid, a sublimed solid
and/or transported by an inert diluent gas into the reactor.
[0033] The reactive agents can be delivered to the reaction chamber
by a variety of means, such as, for example, conventional
cylinders, safe delivery systems, vacuum delivery systems, solid or
liquid-based generators that create the reactive agent at the point
of use. In one embodiment of the present invention, at least one
reactive agent can be added to a non-reactive liquid or gaseous
diluent and applied to the substrate having the substance to be
removed as a spray or other means. The reactive agent can react
with the substance to form the volatile product upon exposure to
one or more energy sources. In an alternative embodiment such as
for chamber cleaning applications, the reactive agent(s) can be
deposited onto a non-reactive support which can be introduced into
the reaction chamber. The material of the non-reactive support is
one that will not react with the reactive agent prior to or during
exposure to one of energy sources. In certain preferred
embodiments, the non-reactive support has a plurality of pores. The
reactive agent(s) can be released upon exposure to one or more
energy sources and react with the substance to be removed to form
the volatile product.
[0034] Since the chlorides of these metals (such as AlCl.sub.3,
HfCl.sub.4, ZrCl.sub.4, and SiCl.sub.4) are more volatile, it is
preferred to convert these high-k substances into chlorides. This
conversion is accomplished by contacting the substance to be
removed with a reactive agent containing chlorine. Preferred
examples of chlorine-containing reactive agents include BCl.sub.3,
COCl.sub.2, HCl, Cl.sub.2, ClF.sub.3, and NF.sub.xCl.sub.3-x, where
x is an integer from 0 to 2, chlorocarbons, and chlorohydrocarbons
(such as C.sub.xH.sub.yCl.sub.z where x is a number ranging from 1
to 6, y is a number ranging from 0 to 13, and z is a number ranging
from 1 to 14). Chlorine-containing reactive agents that also
contain oxygen-getter functions, such as BCl.sub.3, COCl.sub.2,
chlorocarbons and chlorohydrocarbons, are more preferred because
the oxygen-getter component (B, CO, C, or H) in these molecules
extracts oxygen from the high-k materials and hence enhances the
conversion of metal oxides and metal silicates into metal
chlorides. Among the chlorine-containing and oxygen-getter gases,
BCl.sub.3 is the most preferred one. In embodiments employing
COCl.sub.2 as the reactive agent it can be provided in prepared
form or formed by an in situ reaction of CO and Cl.sub.2. In
embodiments for removing metal silicates, the reactive agent can
comprise a chlorine-containing gas and a fluorine-containing gas
(e.g., BCl.sub.3 and BF.sub.3), or a gas containing both fluorine
and chlorine such as ClF.sub.3, and NF.sub.zCl.sub.3, where z is an
integer from 0 to 2.
[0035] In addition to the reactive agents described herein, inert
diluent gases such as nitrogen, CO.sub.2, helium, neon, argon,
krypton, and xenon etc. can also be added. Inert diluent gases can
modify the plasma characteristics and cleaning processes to better
suit some specific applications. The concentration of the inert
gases can range from 0 to 99%.
[0036] The process of the invention is useful for etching
substances from the surfaces of a substrate. Thus, suitable
substrates for the etching embodiments of the invention include,
e.g., semiconductor wafers and the like. FIG. 3 shows a comparison
of the relative etch rate of hafnium oxide, aluminum oxide, and
zirconium oxide for one embodiment of the present invention using
BCl.sub.3 as the reactive agent.
[0037] The present invention may be also suitable for cleaning
substances from substrates such as surfaces of reaction chambers
for CVD and/or ALD processes. The present invention is particularly
suited for removing high k substances that have deposited onto the
exposed surfaces of a reaction chamber such as, for example, the
workpiece platform, grounded sidewalls, and/or showerhead of a
typical reaction chamber.
[0038] Thermal or plasma activation and/or enhancement can
significantly impact the efficacy of dry etching and dry cleaning
of high-k materials. For thermal activation, the substrate can be
heated up to 600.degree. C., more preferably up to 400.degree. C.,
and even more preferably up to 300.degree. C. The pressure range is
generally 10 mTorr to 760 Torr, more preferably 1 Torr to 760
Torr.
[0039] For in situ plasma activation, one can generate the plasma
with a 13.56 MHz RF power supply, with RF power density at least
0.2 W/cm.sup.2, more preferably at least 0.5 W/cm.sup.2, even more
preferably at least 1 W/cm.sup.2. One can also operate the in situ
plasma at RF frequencies lower than 13.56 MHz to enhance ion
assisted cleaning of grounded ALD chamber walls. The operating
pressure is generally in the range of 2.5 mTorr to 100 Torr, more
preferably 5 mTorr to 50 Torr, even more preferably 10 mTorr to 20
Torr. Optionally, one can also combine thermal and plasma
enhancement for more effective cleaning of ALD chamber walls.
[0040] One can also use a remote plasma source to replace an in
situ plasma to generate more reactive species. The remote plasma
source can be generated by either an RF or a microwave source. In
addition, reactions between remote plasma generated reactive
species and high-k materials can be activated/enhanced by heating
ALD reactor components to elevated temperatures up to 600.degree.
C., more preferably up to 400.degree. C., and even more preferably
up to 300.degree. C.
[0041] Other means of activation and enhancement to the cleaning
processes can also be employed. For example, one can use photon
induced chemical reactions to generate reactive species and enhance
the etching/cleaning reactions.
[0042] The following tables show thermochemical calculations for
preferred reactions for volatilizing the substance to be removed
from the substrate. In these tables, K.sub.eq represents the
equilibrium constant for the reaction as written; so that the
larger this value is, the more favorable the reaction will be to
proceed.
1TABLE 1 Al.sub.2O.sub.3 reaction with BCl.sub.3: Al.sub.2O.sub.3 +
2BCl.sub.3(g) B.sub.2O.sub.3 + 2AlCl.sub.3(g) Temperature (.degree.
C.) .DELTA.H (Kcal) .DELTA.S (Cal) .DELTA.G (Kcal) K.sub.eq 0.000
9.561 12.274 6.208 1.078E-005 100.000 9.547 12.249 4.976 1.217E-003
200.000 9.424 11.959 3.766 1.822E-002 300.000 9.299 11.719 2.582
1.036E-001 400.000 9.196 11.553 1.419 3.461E-001 500.000 15.123
19.739 -0.138 1.094E+000 600.000 15.476 20.169 -2.135 3.422E+000
700.000 15.748 20.464 -4.167 8.629E+000 800.000 15.951 20.664
-6.224 1.852E+001 900.000 16.097 20.794 -8.298 3.515E+001 1000.000
16.190 20.871 -10.381 6.056E+001
[0043]
2TABLE 2 HfO.sub.2 reaction with BCl.sub.3: 1.5HfO.sub.2 +
2BCl.sub.3(g) 1.5HfCl.sub.4(g) + B.sub.2O.sub.3 Temperature
(.degree. C.) .DELTA.H (Kcal) .DELTA.S (Cal) .DELTA.G (Kcal)
K.sub.eq 0.000 -17.999 -12.638 -14.547 4.367E+011 25.000 -18.003
-12.653 -14.231 2.707E+010 50.000 -18.025 -12.721 -13.914
2.576E+009 75.000 -18.057 -12.817 -13.595 3.426E+008 100.000
-18.096 -12.924 -13.273 5.950E+007 125.000 -18.138 -13.034 -12.948
1.283E+007 150.000 -18.182 -13.141 -12.621 3.305E+006 175.000
-18.226 -13.242 -12.291 9.879E+005 200.000 -18.268 -13.335 -11.959
3.346E+005
[0044]
3TABLE 3 ZrO.sub.2 reaction with BCl.sub.3: 1.5ZrO.sub.2 +
2BCl.sub.3(g) 1.5ZrCl.sub.4(g) + B.sub.2O.sub.3 Temperature
(.degree. C.) .DELTA.H (Kcal) .DELTA.S (Cal) .DELTA.G (Kcal)
K.sub.eq 0.000 -29.845 -12.107 -26.538 1.717E+021 25.000 -29.825
-12.038 -26.236 1.710E+019 50.000 -29.822 -12.026 -25.935
3.481E+017 75.000 -29.828 -12.047 -25.634 1.239E+016 100.000
-29.842 -12.083 -25.333 6.891E+014 125.000 -29.858 -12.126 -25.030
5.502E+013 150.000 -29.875 -12.168 -24.726 5.913E+012 175.000
-29.892 -12.207 -24.422 8.142E+011 200.000 -29.908 -12.240 -24.116
1.381E+011
[0045]
4TABLE 4 HfO.sub.2 reaction with COCl.sub.2: HfO.sub.2 +
2COCl.sub.2(g) HfCl.sub.4(g) + 2CO.sub.2(g) Temperature (.degree.
C.) .DELTA.H (Kcal) .DELTA.S (Cal) .DELTA.G (Kcal) K.sub.eq 0.000
-20.643 41.960 -32.105 4.890E+025 25.000 -20.649 41.940 -33.153
2.014E+024 50.000 -20.668 41.878 -34.201 1.357E+023 75.000 -20.699
41.787 -35.247 1.343E+022 100.000 -20.739 41.677 -36.290 1.806E+021
125.000 -20.786 41.554 -37.331 3.112E+020 150.000 -20.840 41.423
-38.368 6.578E+019 175.000 -20.900 41.285 -39.402 1.647E+019
200.000 -20.965 41.144 -40.432 4.757E+018
[0046]
5TABLE 5 ZrO.sub.2 reaction with COCl.sub.2: ZrO.sub.2 +
2COCl.sub.2(g) ZrCl.sub.4(g) + 2CO.sub.2(g) Temperature (.degree.
C.) .DELTA.H (Kcal) .DELTA.S (Cal) .DELTA.G (Kcal) K.sub.eq 0.000
-28.540 42.313 -40.098 1.218E+032 25.000 -28.530 42.350 -41.157
1.483E+030 50.000 -28.533 42.341 -42.215 3.573E+028 75.000 -28.547
42.300 -43.273 1.469E+027 100.000 -28.569 42.238 -44.330 9.244E+025
125.000 -28.599 42.160 -45.385 8.215E+024 150.000 -28.636 42.071
-46.438 9.694E+023 175.000 -28.678 41.975 -47.489 1.448E+023
200.000 -28.724 41 .873 -48.537 2.638E+022
[0047]
6TABLE 6 ZrSiO.sub.4 reaction with BCl.sub.3: ZrSiO.sub.4 +
2.667BCl.sub.3(g) SiCl.sub.4(g) + ZrCl.sub.4(g) +
1.333B.sub.2O.sub.3 Temperature (.degree. C.) .DELTA.H (Kcal)
.DELTA.S (Cal) .DELTA.G (Kcal) K.sub.eq 0.000 -31.065 -21.096
-25.303 1.764E+020 25.000 -31.003 -20.879 -24.778 1.460E+018 50.000
-30.962 -20.747 -24.258 2.554E+016 75.000 -30.935 -20.665 -23.740
8.020E+014 100.000 -30.916 -20.613 -23.224 4.013E+013 125.000
-30.902 -20.577 -22.710 2.928E+012 150.000 -30.891 -20.549 -22.196
2.914E+011 175.000 -30.879 -20.523 -21.682 3.755E+010 200.000
-30.867 -20.496 -21.169 6.012E+009 225.000 -30.852 -20.466 -20.657
1.158E+009 250.000 -30.835 -20.432 -20.146 2.612E+008 275.000
-30.814 -20.393 -19.636 6.754E+007 300.000 -30.790 -20.349 -19.127
1.967E+007 325.000 -30.761 -20.300 -18.618 6.358E+006 350.000
-30.729 -20.247 -18.112 2.252E+006 375.000 -30.692 -20.190 -17.606
8.652E+005 400.000 -30.652 -20.130 -17.102 3.572E+005 425.000
-30.608 -20.066 -16.600 1.573E+005 450.000 -22.891 -9.391 -16.100
7.349E+004 475.000 -22.663 -9.081 -15.869 4.327E+004 500.000
-22.443 -8.791 -15.646 2.649E+004
[0048]
7TABLE 7 ZrSiO.sub.4 reaction with BF.sub.3 and BCl.sub.3:
ZrSiO.sub.4 + 1.333BF.sub.3(g) + 1.333BCl.sub.3(g) SiF.sub.4(g) +
ZrCl.sub.4(g) + 1.333B.sub.2O.sub.3 Temperature (.degree. C.)
.DELTA.H (Kcal) .DELTA.S (Cal) .DELTA.G (Kcal) K.sub.eq 0.000
-25.010 -21.014 -19.270 2.627E+015 25.000 -24.951 -20.807 -18.748
5.540E+013 50.000 -24.912 -20.681 -18.229 2.136E+012 75.000 -24.885
-20.600 -17.713 1.319E+011 100.000 -24.865 -20.545 -17.199
1.186E+010 125.000 -24.849 -20.502 -16.686 1.445E+009 150.000
-24.833 -20.463 -16.174 2.260E+008 175.000 -24.816 -20.423 -15.663
4.354E+007 200.000 -24.796 -20.380 -15.153 9.992E+006 225.000
-24.772 -20.332 -14.644 2.661E+006 250.000 -24.745 -20.278 -14.136
8.053E+005 275.000 -24.712 -20.218 -13.630 2.721E+005 300.000
-24.675 -20.152 -13.125 1.012E+005 325.000 -24.633 -20.080 -12.622
4.095E+004 350.000 -24.586 -20.003 -12.121 1.784E+004 375.000
-24.535 -19.922 -11.622 8.303E+003 400.000 -24.478 -19.837 -11.125
4.095E+003 425.000 -24.418 -19.749 -10.630 2.128E+003 450.000
-16.684 -9.050 -10.139 1.160E+003 475.000 -16.439 -8.717 -9.917
7.894E+002 500.000 -16.201 -8.405 -9.703 5.535E+002
[0049] Tables 1-7 show that BCl.sub.3 and COCl.sub.2 can be used as
the etchants for dry etching and cleaning of the high-k materials.
BCl.sub.3 (boron trichloride) is a liquefied gas at room
temperature and can be readily delivered into ALD reactors for
chamber cleaning. COCl.sub.2 (phosgene) is preferably provided in
situ in etch or deposition reactors by reacting gaseous carbon
monoxide and chlorine to form phosgene assisted by an external
energy source (e.g. plasma) as follows:
CO(g)+Cl.sub.2(g).fwdarw.COCl.sub.2
[0050] In other embodiments of the present invention such as
applications that are sensitive to boron residue, chlorocarbons
(CC) and hydrochlorocarbons (HCC) may be employed as the reactive
agent because these compounds may contain chlorine as well as
oxygen getter components (C or H). The general formula for the CC
and HCC compounds is C.sub.xH.sub.yCl.sub.z, where x ranges from 1
to 6, y ranges from 0 to 13, and z ranges from 1 to 14. Examples of
suitable CC and HCC compounds include, but are not limited to,
trans-dichloroethylene C.sub.2H.sub.2Cl.sub.2 (a.k.a.
Trans-LC.RTM.), cis-dichloroethylene, 1,1-dichloroethylele,
1,1,1-trichloroethane (C.sub.2H.sub.3Cl.sub.3), or
tetrachloroethylene C.sub.2Cl.sub.4, C.sub.4H.sub.4Cl.sub.4,
CHCl.sub.3, and CCl.sub.4. Some CC and HCC compounds may react with
high-k metal oxides without the addition of oxygen. For example, in
some embodiments, tetrachloroethylene (C.sub.2Cl.sub.4) can react
with Al.sub.2O.sub.3 to form volatile byproducts as follows:
1.5C.sub.2Cl.sub.4(g)+Al.sub.2O.sub.3.fwdarw.2AlCl.sub.3(g)+3CO(g)
[0051] Table 8 illustrates that the reaction is thermodynamically
favorable at temperatures above 100.degree. C.
8TABLE 8 Thermodynamic data for reaction: 1.5C.sub.2Cl.sub.4(g) +
Al.sub.2O.sub.3 = 2AlCl.sub.3(g) + 3CO(g) T (.degree. C.) .DELTA.H
(Kcal) .DELTA.S (Cal) .DELTA.G (Kcal) K.sub.eq 0.000 46.723 157.382
3.734 1.028E-003 100.000 46.760 157.552 -12.031 1.114E+007 200.000
46.314 156.508 -27.738 6.509E+012 300.000 45.599 155.144 -43.322
3.317E+016 400.000 44.704 153.709 -58.765 1.204E+019 500.000 43.674
152.284 -74.064 8.667E+020 600.000 42.541 150.907 -89.223
2.160E+022 700.000 41.340 149.605 -104.248 2.594E+023 800.000
40.087 148.380 -119.147 1.848E+024 900.000 38.793 147.228 -133.927
8.948E+024 1000.000 37.467 146.143 -148.595 3.236E+025
[0052] The above thermochemical calculations are illustrations of
limiting cases for those chemical reactions. In addition to the
limiting case reaction products such as B.sub.2O.sub.3,
intermediate reaction products such as boron oxychloride (BOCl) can
also be formed in reactions between high-k materials and BCl.sub.3.
Intermediate reaction products such as BOCl have higher volatility
and thus may further enhance the removal of high-k materials.
[0053] Other CC and HCC compounds may need the addition of oxygen
to release chlorine without forming carbon residues (soot). For
example, trans-dichloroethylene (C.sub.2H.sub.2Cl.sub.2) (a.k.a.
Trans-LC.RTM.) can react with Al.sub.2O.sub.3 at an
O.sub.2:C.sub.2H.sub.2Cl.sub.2 molar ration of 2:1,
60.sub.2(g)+Al.sub.2O.sub.3+3C.sub.2H.sub.2Cl.sub.2(g)=2Al-
Cl.sub.3(g)+6CO.sub.2(g)+3H.sub.2O(g) Table 9 shows such a reaction
is thermodynamically favorable at temperatures between 0 and
1000.degree. C.
9TABLE 9 Thermodynamic data for reaction: 6O.sub.2(g) +
Al.sub.2O.sub.3 + 3C.sub.2H.sub.2Cl.sub.2(g) = 2AlCl.sub.3(g) +
6CO.sub.2(g) + 3H.sub.2O(g) T (.degree. C.) .DELTA.H (Kcal)
.DELTA.S (Cal) .DELTA.G (Kcal) K.sub.eq 0.000 -616.464 77.981
-637.764 1.000E+308 100.000 -616.428 78.113 -645.576 1.000E+308
200.000 -616.656 77.585 -653.365 6.559E+301 300.000 -617.145 76.654
-661.079 1.257E+252 400.000 -617.872 75.490 -668.688 1.316E+217
500.000 -618.811 74.193 -676.173 1.422E+191 600.000 -619.918 72.848
-683.525 1.261E+171 700.000 -621.140 71.523 -690.743 1.380E+155
800.000 -622.440 70.253 -697.832 1.340E+142 900.000 -623.784 69.056
-704.796 2.040E+131 1000.000 -625.138 67.947 -711.646
1.485E+122
[0054] An excess amount of oxygen is undesirable in the above
reactions since excess O.sub.2 can convert metal chlorides back to
metal oxides. A better way to prevent excess oxygen is to oxidize
carbon only partially into CO by running the reaction under an
oxygen lean condition. For example, O.sub.2:C.sub.2H.sub.2Cl.sub.2
molar ratio of 1:1 can lead to the formation of CO and AlCl.sub.3
as the byproducts:
3C.sub.2H.sub.2Cl.sub.2(g)+Al.sub.2O.sub.3+3O.sub.2=2AlCl.sub.3(g)+6CO(g)+-
3H.sub.2O(g)
[0055] As shown in Table 10, such partial oxidation reaction is
also favorable thermodynamically.
10TABLE 10 Thermodynamic data for reaction:
3C.sub.2H.sub.2Cl.sub.2(g) + Al.sub.2O.sub.3 + 3O.sub.2 =
2AlCl.sub.3(g) + 6CO(g) + 3H.sub.2O(g) T (.degree. C.) .DELTA.H
(Kcal) .DELTA.S (Cal) .DELTA.G (Kcal) K.sub.eq 0.000 -210.973
200.961 -265.865 5.480E+212 100.000 -210.103 203.760 -286.136
3.984E+167 200.000 -210.055 203.905 -306.532 3.982E+141 300.000
-210.561 202.949 -326.881 4.512E+124 400.000 -211.485 201.470
-347.105 5.046E+112 500.000 -212.749 199.725 -367.166 6.267E+103
600.000 -214.276 197.870 -387.046 7.688E+096 700.000 -215.992
196.011 -406.740 2.255E+091 800.000 -217.847 194.197 -426.250
6.518E+086 900.000 -219.797 192.461 -445.582 1.037E+083 1000.000
-221.800 190.822 -464.745 6.097E+079
[0056] Instead of oxygen, chlorine (Cl.sub.2) can be added to
prevent the formation of carbon soot. For example,
Cl.sub.2:C.sub.2H.sub.2Cl.sub.2 molar ratio of 2:1 allows the
following reaction:
2Cl.sub.2(g)+Al.sub.2O.sub.3+C.sub.2H.sub.2Cl.sub.2(g)=2AlCl.sub.3(g)+H.su-
b.2O(g).degree.2CO(g)
[0057] Similarly, Cl.sub.2:C.sub.2H.sub.2Cl.sub.2 molar ratio of
4:1 allows the following reaction:
4Cl.sub.2(g)+Al.sub.2O.sub.3+C.sub.2H.sub.2Cl.sub.2(g)=3.333AlCl.sub.3(g)+-
H.sub.2O(g)+2CO.sub.2(g)
[0058] Both reactions are thermodynamically favorable, as shown in
Tables 11 and 12. The use of chlorine to control soot formation is
more desirable since excess amount of chlorine helps the
chlorination of metal oxides.
11TABLE 11 Thermodynamic data for reaction: 2Cl.sub.2(g) +
Al.sub.2O.sub.3 + C.sub.2H.sub.2Cl.sub.2(g) = 2AlCl.sub.3(g) +
H.sub.2O(g) + 2CO(g) T (.degree. C.) .DELTA.H (kcal) .DELTA.S
(kcal) .DELTA.G (kcal) K.sub.eq 0.000 10.291 101.403 -17.407
8.479E+013 100.000 10.619 102.465 -27.616 1.498E+016 200.000 10.554
102.326 -37.861 3.088E+017 300.000 10.225 101.701 -48.065
2.135E+018 400.000 9.697 100.855 -58.194 7.859E+018 500.000 9.005
99.900 -68.233 1.946E+019 600.000 8.185 98.904 -78.173 3.701E+019
700.000 7.277 97.920 -88.014 5.858E+019 800.000 6.303 96.967
-97.758 8.134E+019 900.000 5.280 96.056 -107.409 1.026E+020
1000.000 4.224 95.193 -116.971 1.205E+020
[0059]
12TABLE 12 Thermodynamic data for reaction: 4Cl.sub.2(g) +
Al.sub.2O.sub.3 + C.sub.2H.sub.2Cl.sub.2(g) = 3.333AlCl.sub.3(g) +
H.sub.2O(g) + 2CO.sub.2(g) T (.degree. C.) .DELTA.H (kcal) .DELTA.S
(kcal) .DELTA.G (kcal) K.sub.eq 0.000 -44.076 94.797 -69.970
9.734E+055 100.000 -43.990 95.096 -79.475 3.562E+046 200.000
-44.229 94.542 -88.962 1.245E+041 300.000 -44.715 93.617 -98.372
3.262E+037 400.000 -45.399 92.520 -107.680 9.182E+034 500.000
-46.255 91.338 -116.873 1.096E+033 600.000 -47.248 90.132 -125.946
3.365E+031 700.000 -48.328 88.961 -134.900 1.988E+030 800.000
-49.475 87.840 -143.740 1.886E+029 900.000 -50.671 86.775 -152.470
2.550E+028 1000.000 -51.901 85.769 -161.097 4.532E+027
[0060] In addition to the chloride compounds, the bromide and
iodide compounds of these high-k materials, such as AlBr.sub.3,
AlI.sub.3, HfBr.sub.4, Hfl.sub.4, ZrBr.sub.4, and Zrl.sub.4 have a
volatility similar to their corresponding chlorides. Therefore,
some bromo- and iodo-compounds can also be used to etch/clean these
high-k materials. Bromine and iodine ions are heavier than chlorine
ions, hence bromine and iodine ions can provide more effective
sputtering to energize plasma-assisted etch/clean reactions with
high-k materials. Bromine and iodine atoms have higher surface
sticking coefficients than chlorine atoms. A higher sticking
coefficient relates to a higher probability for bromine and iodine
atoms/ions to be adsorbed onto the surface of high-k materials
hence enhancing the bromination/iodization reactions. Desirable
bromo- and iodo-compounds preferably contain an oxygen-getter
function in the molecule. Examples of suitable bromine and iodine
containing compounds include boron tribromide (BBr.sub.3), boron
triiodide (BI.sub.3), hydrogen bromide (HBr), hydro iodide (HI),
bromocarbons such as CBr.sub.4, bromohydrocarbons such as
trans-dibromoethylene (C.sub.2H.sub.2Br.sub.2), iodocarbons such as
Cl.sub.4, and iodohydrocarbons such as trans-diiodoethylene
(C.sub.2H.sub.2I.sub.2) etc. For HfO.sub.2, the bromine and iodine
chemistries are dramatically more favorable than the corresponding
chlorine chemistry, as shown in tables 13-15.
13TABLE 13 Thermodynamic data for reaction: 1.5HfO.sub.2 +
2BCl.sub.3(g) = 1.5HfCl.sub.4(g) + B.sub.2O.sub.3 T (.degree. C.)
.DELTA.H (kcal) .DELTA.S (kcal) .DELTA.G (kcal) K.sub.eq 0.000
-17.999 -12.638 -14.547 4.367E+011 100.000 -18.096 -12.924 -13.273
5.950E+007 200.000 -18.268 -13.335 -11.959 3.346E+005 300.000
-18.413 -13.614 -10.611 1.113E+004 400.000 -18.507 -13.765 -9.241
1.001E+003 500.000 -12.540 -5.525 -8.268 2.175E+002 600.000 -12.126
-5.020 -7.743 8.672E+001 700.000 -11.790 -4.655 -7.260 4.271E+001
800.000 -11.524 -4.395 -6.808 2.436E+001 900.000 -11.321 -4.213
-6.378 1.543E+001 1000.000 -11.176 -4.094 -5.963 1.056E+001
[0061]
14TABLE 14 Thermodynamic data for reaction: 1.5HfO.sub.2 +
2BBr.sub.3(g) = 1.5HfBr.sub.4(g) + B.sub.2O.sub.3 T (.degree. C.)
.DELTA.H (kcal) .DELTA.S (kcal) .DELTA.G (kcal) K.sub.eq 0.000
-53.997 -10.093 -51.241 1.003E+041 100.000 -54.122 -10.459 -50.219
2.602E+029 200.000 -54.371 -11.049 -49.143 5.026E+022 300.000
-54.601 -11.492 -48.014 2.042E+018 400.000 -54.773 -11.770 -46.850
1.629E+015 500.000 -48.872 -3.621 -46.073 1.058E+013 600.000
-48.508 -3.178 -45.734 2.806E+011 700.000 -48.207 -2.851 -45.433
1.600E+010 800.000 -47.960 -2.609 -45.161 1.577E+009 900.000
-47.761 -2.431 -44.909 2.328E+008 1000.000 -47.606 -2.304 -44.673
4.669E+007
[0062]
15TABLE 15 Thermodynamic data for reaction: 1.5HfO.sub.2 +
2Bl.sub.3(g) = 1.5Hfl.sub.4(g) + B.sub.2O.sub.3 T (.degree. C.)
.DELTA.H (kcal) .DELTA.S (kcal) .DELTA.G (kcal) K.sub.eq 0.000
-58.042 -15.921 -53.694 9.212E+042 100.000 -58.342 -16.842 -52.057
3.104E+030 200.000 -58.692 -17.675 -50.329 1.775E+023 300.000
-58.991 -18.250 -48.531 3.214E+018 400.000 -59.216 -18.614 -46.686
1.442E+015 500.000 -53.362 -10.530 -45.221 6.080E+012 600.000
-53.042 -10.139 -44.189 1.152E+011 700.000 -52.784 -9.859 -43.190
5.015E+009 800.000 -52.581 -9.660 -42.214 3.961E+008 900.000
-52.429 -9.524 -41.256 4.856E+007 1000.000 -52.324 -9.438 -40.308
8.315E+006
[0063] Similarly, bromine and iodine chemistries are also
thermodynamically favorable for reactions with Al.sub.2O.sub.3 and
ZrO.sub.2, as shown in Tables 16-18.
16TABLE 16 Thermodynamical data for reaction: 2BBr.sub.3(g) +
Al.sub.2O.sub.3 = 2AlBr.sub.3(g) + B.sub.2O.sub.3 T (.degree. C.)
.DELTA.H (kcal) .DELTA.S (kcal) .DELTA.G (kcal) K.sub.eq 0.000
-2.212 12.687 -5.678 3.493E+004 100.000 -2.279 12.503 -6.944
1.168E+004 200.000 -2.482 12.022 -8.170 5.945E+003 300.000 -2.685
11.632 -9.352 3.683E+003 400.000 -2.852 11.362 -10.501 2.567E+003
500.000 3.023 19.476 -12.035 2.525E+003 600.000 3.337 19.858
-14.003 3.200E+003 700.000 3.579 20.122 -16.003 3.928E+003 800.000
3.764 20.303 -18.024 4.688E+003 900.000 3.897 20.422 -20.061
5.464E+003 1000.000 3.985 20.494 -22.107 6.241E+003
[0064]
17TABLE 17 Thermodynamical data for reaction: 2BBr.sub.3(g) +
1.5ZrO.sub.2 = 1.5ZrBr.sub.4(g) + B.sub.2O.sub.3 T (.degree. C.)
.DELTA.H (kcal) .DELTA.S (kcal) .DELTA.G (kcal) K.sub.eq 0.000
-44.096 -11.573 -40.935 5.691E+032 100.000 -44.194 -11.861 -39.768
1.965E+023 200.000 -44.363 -12.264 -38.560 6.495E+017 300.000
-44.489 -12.509 -37.320 1.706E+014 400.000 -44.545 -12.600 -36.064
5.125E+011 500.000 -38.522 -4.282 -35.212 9.000E+009 600.000
-38.033 -3.686 -34.815 5.186E+008 700.000 -37.604 -3.220 -34.470
5.520E+007 800.000 -37.229 -2.853 -34.167 9.096E+006 900.000
-36.902 -2.561 -33.897 2.067E+006 1000.000 -36.619 -2.330 -33.653
5.989E+005
[0065]
18TABLE 18 Thermodynamical data for reaction: 2Bl.sub.3(g) +
1.5ZrO.sub.2 = 1.5Zrl.sub.4(g) + B.sub.2O.sub.3 T (.degree. C.)
.DELTA.H (kcal) .DELTA.S (kcal) .DELTA.G (kcal) K.sub.eq 0.000
-74.430 -11.695 -71.235 1.001E+057 100.000 -74.587 -12.171 -70.045
1.067E+041 200.000 -74.805 -12.689 -68.801 6.053E+031 300.000
-74.972 -13.013 -67.514 5.573E+025 400.000 -75.065 -13.163 -66.204
3.134E+021 500.000 -69.074 -4.891 -65.293 2.873E+018 600.000
-68.614 -4.330 -64.833 1.695E+016 700.000 -68.212 -3.894 -64.423
2.947E+014 800.000 -67.861 -3.549 -64.052 1.110E+013 900.000
-67.555 -3.276 -63.711 7.411E+011 1000.000 -67.291 -3.061 -63.394
7.642E+010
[0066] In certain embodiments, the reactive agent may comprise a
chelating compound. A chelating compound, as used herein, describes
a compound that contains at least two electron-rich (e.g., Lewis
base) sites that could potentially interact with an
electron-deficient (e.g., Lewis acid) metal atom such as, but not
limited to, Zr, Al, or Hf. It is not required, however, that the
plurality of sites simultaneously interact with the metal in order.
Also, the chelating compound may be delivered into the reaction
chamber as a conjugate acid of the basic site. Examples of these
compounds may be found in U.S. Pat. No. 3,634,477. Further examples
of chelating compounds include oxy-halocarbon compounds, such as
chloroacetic acid, oxalyl chloride, etc., are known to be chelating
compounds or agents that can react with metal oxides and metal
chlorides to form volatile byproducts. Some exemplary chelating
compounds may have the formula
C.sub..alpha.H.sub..beta.X.sub..gamma.Y.sub.67 O.sub.68 , wherein X
and Y are one of the halogen atoms F, Cl, Br, and l; .alpha. is a
number ranging from 1 to 6, .beta. is a number ranging from 0 to
13, the sum of .gamma.+.delta. is a number ranging from 1 to 14,
and .epsilon. is a number ranging from 1 to 6. Examples of these
compounds include hexafluoropetanedione
(CCl.sub.3C(O)CH.sub.2C(O)CCl.sub.3) (a.k.a. Hhfac),
hexachloropetanedione (CCl.sub.3C(O)CH.sub.2C(O)CCl.sub.3- ),
hexafluoroacetone (CF.sub.3C(O)CF.sub.3) and hexachloroacetone
(CCl.sub.3C(O)CCl.sub.3). For example, hexafluoropetanedione
(a.k.a. Hhfac) (CF.sub.3C(O)CH.sub.2C(O)CF.sub.3, or
C.sub.5H.sub.2O.sub.2F.sub.6- ) is a common chelating agent that
can react with a wide variety of metal oxides and/or chlorides to
form volatile organo-metal compounds M(hfac).sub.x, where M is a
metal ion such as Al.sup.3+, Hf.sup.4+, and Zr.sup.4+ etc. Such
chelating property can be used to enhance the etching and chamber
cleaning of high-k materials. In addition, these molecules can be
used as an oxygen scavenger to enhance chlorination of the high-k
materials. For example, one can have:
HfO.sub.2+C.sub.5H.sub.2O.sub.2F.sub.6+2Cl.sub.2+O.sub.2=HfCl.sub.4(g)+H.s-
ub.2O(g)+3COF.sub.2(g)+2CO(g)
[0067] In certain embodiments of the present invention, the
chlorine analog of Hhfac, hexachloropetanedione
(CCl.sub.3C(O)CH.sub.2C(O)CCl.sub.- 3) may be more advantageous as
the reactive agent since it can be both an oxygen scavenger and a
chlorinating agent. These reactions can be also be assisted by
thermal and/or plasma activation. For example,
C.sub.5H.sub.2O.sub.2Cl.sub.6+Al.sub.2O.sub.3+0.5O.sub.2=2AlCl.sub.3(g)+5C-
O(g)+H.sub.2O(g)
[0068] and
2C.sub.5H.sub.2O.sub.2Cl.sub.6+3HfO.sub.2+O.sub.2=3HfCl.sub.4(g)+10CO(g)+2-
H.sub.2 2O(g)
[0069] To prevent oxidation of the metal chlorides, chlorine can be
used to replace oxygen:
C.sub.5H.sub.2O.sub.2Cl.sub.6+Al.sub.2O.sub.3+Cl.sub.2=2AlCl.sub.3(g)+5CO(-
g)+2HCl(g)
[0070] Chlorosilanes, hydrochlorosilanes, and organochlorosilanes
can also be effective agents to etch/clean high-k materials. Thanks
to the highly stable SiO.sub.2 byproduct, these compounds can be
both a very effective oxygen scavenger and a chlorinating agent.
Upon exposure to a thermal or plasma source, these compounds can be
just as effective as BCl.sub.3 to convert high-k materials into
volatile chlorides without the potential problem of boron residue
contamination. In certain embodiments, the chlorosilane,
hydrochlorosilane, or organochlorosilane compound has the formula
Si.sub.pCl.sub.qR.sub.sH.sub.t, wherein: 1.ltoreq.p.ltoreq.3,
1.ltoreq.q.ltoreq.{2p+2-(s+t)}, s and t can have any values subject
to the constraint that 0.ltoreq.(s+t).ltoreq.(2p+1) and R is an
organic radical having 1-8 carbon atoms, including: hydrocarbyl
(e.g. methyl, ethyl, phenyl, p-tolyl), halocarbyl (e.g.,
trichloromethyl, trifluoromethyl, pentafluoroethyl), halogenated
hydrocarbyl (e.g., chloromethyl, 2,4-difluorophenyl), oxygenated
hydrocarbyl (e.g., methoxy, hydroxyethyl, chlorormethoxy) and
nitrogen-substituted hydrocarbyl moieties (e.g., aminomethyl,
dimethylaminonomethyl, pyridyl). Exemplary reactions include:
1.5SiCl.sub.4(g)+Al.sub.2O.sub.3=2AlCl.sub.3(g)+1.5SiO.sub.2
SiCl.sub.4(g)+HfO.sub.2=HfCl.sub.4(g)+SiO.sub.2
SiCl.sub.4(g)+ZrO.sub.2=ZrCl.sub.4(g)+SiO.sub.2
O.sub.2(g)+2SiHCl.sub.3(g)+Al.sub.2O.sub.3=2AlCl.sub.3(g)+H.sub.2O(g)+2SiO-
.sub.2
4O.sub.2(g)+2SiCH.sub.3Cl.sub.3(g)+Al.sub.2O.sub.3=2AlCl.sub.3(g)+3H.sub.2-
O(g)+2SiO.sub.2+2CO.sub.2(g)
[0071] Thermodynamic calculations show that the above reactions are
favorable at room temperature or moderately elevated temperatures,
as shown in Tables 19-23.
19TABLE 19 Thermodynamical data for reaction: 1.5SiCl.sub.4(g) +
Al.sub.2O.sub.3 = 2AlCl.sub.3(g) + 1.5SiO.sub.2 T (.degree. C.)
.DELTA.H (kcal) .DELTA.S (kcal) .DELTA.G (kcal) K.sub.eq 0.000
32.037 34.471 22.621 7.927E-019 100.000 31.880 33.990 19.196
5.703E-012 200.000 31.647 33.439 15.825 4.895E-008 300.000 31.400
32.967 12.506 1.702E-005 400.000 31.178 32.608 9.228 1.009E-003
500.000 31.009 32.373 5.980 2.039E-002 600.000 31.097 32.475 2.742
2.059E-001 700.000 30.702 32.047 -0.484 1.285E+000 800.000 30.291
31.645 -3.669 5.587E+000 900.000 30.612 31.957 -6.878 1.912E+001
1000.000 30.204 31.623 -10.057 5.327E+001
[0072]
20TABLE 20 Thermodynamical data for reaction: SiCl.sub.4(g) +
HfO.sub.2 =HfCl.sub.4(g) + SiO.sub.2 T (.degree. C.) .DELTA.H
(kcal) .DELTA.S (kcal) .DELTA.G (kcal) K.sub.eq 0.000 2.985 6.373
1.244 1.010E-001 100.000 2.825 5.878 0.631 4.267E-001 200.000 2.636
5.430 0.067 9.314E-001 300.000 2.459 5.089 -0.458 1.495E+000
400.000 2.317 4.860 -0.955 2.042E+000 500.000 2.230 4.739 -1.434
2.543E+000 600.000 2.330 4.857 -1.911 3.009E+000 700.000 2.110
4.618 -2.385 3.432E+000 800.000 1.877 4.391 -2.835 3.779E+000
900.000 2.130 4.633 -3.306 4.129E+000 1000.000 1.892 4.439 -3.759
4.419E+000
[0073]
21TABLE 21 Thermodynamical data for reaction: SiCl.sub.4(g) +
ZrO.sub.2 = ZrCl.sub.4(g) + SiO.sub.2 T (.degree. C.) .DELTA.H
(kcal) .DELTA.S (kcal) .DELTA.G (kcal) K.sub.eq 0.000 -4.912 6.726
-6.749 2.516E+005 100.000 -5.006 6.439 -7.408 2.185E+004 200.000
-5.123 6.160 -8.038 5.164E+003 300.000 -5.226 5.963 -8.643
1.977E+003 400.000 -5.288 5.861 -9.233 9.955E+002 500.000 -5.292
5.854 -9.818 5.966E+002 600.000 -5.106 6.077 -10.412 4.041E+002
700.000 -5.237 5.936 -11.013 2.975E+002 800.000 -5.375 5.800
-11.600 2.304E+002 900.000 -5.026 6.129 -12.216 1.887E+002 1000.000
-5.163 6.016 -12.823 1.590E+002
[0074]
22TABLE 22 Thermodynamical data for reaction: O.sub.2(g) +
2SiHCl.sub.3(g) + Al.sub.2O.sub.3 = 2AlCl.sub.3(g) + H.sub.2O(g) +
2SiO.sub.2 T (.degree. C.) .DELTA.H (kcal) .DELTA.S (kcal) .DELTA.G
(kcal) K.sub.eq 0.000 -134.894 4.620 -136.156 8.893E+108 100.000
-135.412 2.993 -136.529 9.339E+079 200.000 -135.834 1.989 -136.775
1.521E+063 300.000 -136.187 1.309 -136.938 1.662E+052 400.000
-136.464 0.863 -137.045 3.145E+044 500.000 -136.643 0.612 -137.117
5.789E+038 600.000 -136.462 0.826 -137.183 2.187E+034 700.000
-136.917 0.333 -137.241 6.669E+030 800.000 -137.387 -0.126 -137.251
8.991E+027 900.000 -136.875 0.364 -137.301 3.806E+025 1000.000
-137.329 -0.008 -137.319 3.752E+023
[0075]
23TABLE 23 Thermodynamical data for reaction: 4O.sub.2(g) +
2SiCH.sub.3Cl.sub.3(g) + Al.sub.2O.sub.3 = 2AlCl.sub.3(g) +
3H.sub.2O(g) + 2SiO.sub.2 + 2CO.sub.2(g) T (.degree. C.) .DELTA.H
(kcal) .DELTA.S (kcal) .DELTA.G (kcal) K.sub.eq 0.000 -423.175
31.434 -431.762 1.000E+308 100.000 -423.093 31.710 -434.925
5.650E+254 200.000 -423.197 31.470 -438.087 2.349E+202 300.000
-423.424 31.038 -441.213 1.797E+168 400.000 -423.714 30.573
-444.294 1.818E+144 500.000 -424.016 30.154 -447.329 2.878E+126
600.000 -424.028 30.132 -450.339 5.361E+112 700.000 -424.723 29.380
-453.314 6.510E+101 800.000 -425.461 28.658 -456.216 8.264E+092
900.000 -425.237 28.892 -459.132 3.469E+085 1000.000 -425.990
28.276 -461.990 2.051E+079
[0076] In addition, other chloride compounds such as GeCl.sub.4 and
related compounds can also be used to etch/clean high-k materials
in a similar manner. When etching/cleaning hafnium and zirconium
based high-k materials, AlCl.sub.3 can be added into the reactants
to enhance the chlorination of HfO.sub.2, ZrO.sub.2,
HfSi.sub.xO.sub.y, and ZrSi.sub.xO.sub.y etc. This is because
AlCl.sub.3 can be used as an oxygen scavenger to facilitate the
chlorination of HfO.sub.2 and ZrO.sub.2 etc. while forming aluminum
oxychloride such as AlOCl, which is more volatile than
Al.sub.2O.sub.3.
[0077] In addition to being thermodynamically favorable, a chemical
reaction often requires an external energy source to overcome an
activation energy barrier so that the reaction can proceed. The
external energy source can be, for example, thermal heating or
plasma activation. Higher temperatures can accelerate chemical
reactions and make reaction byproducts more volatile. However,
there may be practical limitations on temperature in production
deposition chambers. Plasmas can generate more reactive species to
facilitate reactions. Ions in the plasmas are accelerated by the
electric field in the plasma sheath to gain energy. Energetic ions
impinging upon surfaces can provide the energy needed to overcome
reaction activation energy barrier. Ion bombardment also helps to
volatize and remove reaction byproducts. These are common
mechanisms in plasma etching/cleaning and reactive ion etching.
Optionally, one can combine both thermal and plasma activation
mechanisms to enhance the desired reactions for dry
etching/cleaning of high-k materials. As an alternative to in situ
plasma cleaning, one can use remote plasma source to generate more
reactive species for cleaning high-k material residues from the
deposition chambers. In addition, reactions between remote plasma
generated reactive species and high-k materials can be activated
and/or enhanced by heating CVD or ALD reactor components to
elevated temperatures up to 600.degree. C., more preferably up to
400.degree. C., and even more preferably up to 300.degree. C.
[0078] FIGS. 1a and 1b provides an illustration of an apparatus
suitable for performing chamber cleaning using an internal energy
source or an external energy source, respectively. In FIG. 1a, the
reactive agent (i.e., BCl.sub.3) is introduced into the substrate
(i.e., reaction chamber) which has the substance to be removed or
the high-k residues such as the HfO.sub.2 depicted. As shown in
FIG. 1a, the substance is deposited upon at least a portion of the
exposed surface within the reaction chamber, particularly, the
grounded sidewalls, shower head, work piece platform, etc. The
reactive agent is exposed to an external energy source, such as the
RF power supply or heater shown, which creates active species such
as BCl.sub.3 and Cl. The active species react with substance and
form a volatile product such as HfCl.sub.4. The volatile product is
removed from the chamber as shown.
[0079] FIG. 1b provides an example of an apparatus wherein the
reactive agent is exposed to an external energy source such as a
microwave source to produce a high density plasma of the reactive
agent. The high density plasma can then be transported to the
substrate (i.e., reaction chamber) having the substance to be
removed and form the volatile product. The volatile product can be
easily removed form the chamber via the foreline shown.
EXAMPLES
[0080] The invention will be illustrated in more detail with
reference to the following Examples, but it should be understood
that the present invention is not deemed to be limited thereto.
[0081] The following are experimental examples of utilizing the
above chemistries for dry etching/cleaning of high-k materials. The
experiments for examples 1 through 3 were conducted in a parallel
plate capacitively coupled RF plasma reactorsimilar to the setup
illustrated in FIG. 2. Sample coupons were prepared from wafers
coated with high-k dielectric materials Al.sub.2O.sub.3, HfO.sub.2,
and ZrO.sub.2 deposited by atomic layer deposition. For each
experimental run, a sample coupon was put onto a carrier wafer and
loaded onto the reactor chuck through a loadlock. Process gases
were fed into the reactor from a top mounted showerhead. The chuck
was then powered by a 13.56 MHz RF power source to generate the
plasma. The thickness of the high-k film on a coupon was measured
by ellipsometry both before and after a timed exposure of the
processing plasma. Change in high-k film thickness after plasma
processing is used to calculate the etch rate. In addition to etch
rate, plasma dc self bias voltage (V.sub.bias) was also measured.
In examples 1-3, both the wafer and the chamber walls were kept at
room temperature.
Example 1
[0082] Plasma Etching/Cleaning of Al.sub.2O.sub.3 Samples
[0083] Since power is one of the key processing parameters in
plasma etching/cleaning, we evaluated power dependence of
Al.sub.2O.sub.3 etching by BCl.sub.3 plasma. The results are listed
in Table 24 below.
24TABLE 24 RF power dependence of Al.sub.2O.sub.3 etching by
BCl.sub.3 plasma Power density Pressure Al.sub.2O.sub.3 etch rate
V.sub.bias Power (W) (W/cm.sup.2) (mTorr) (nm/min) (V) 50 0.27 500
0.0 16 100 0.55 500 3.0 35 200 1.10 500 9.8 58
[0084] Apparently there is a threshold power density of 0.55
W/cm.sup.2 or threshold V.sub.bias of 35 V for etching
Al.sub.2O.sub.3. Higher power density and higher V.sub.bias
resulted in higher etch rate.
[0085] Next, we investigated chamber pressure dependence of
Al.sub.2O.sub.3 etching by BCl.sub.3 plasma. The results are listed
in Table 25 below.
25TABLE 25 Chamber pressure dependence of Al.sub.2O.sub.3 etching
by BCl.sub.3 plasma Power density Pressure Al.sub.2O.sub.3 etch
rate V.sub.bias Power (W) (W/cm.sup.2) (mTorr) (nm/min) (V) 100
0.55 50 7.2 91 100 0.55 500 3.0 35 100 0.55 1000 0.8 4
[0086] A higher etch rate was achieved at a reduced pressure. There
are two factors that favor the etch reactions at reduced pressure.
First, higher bias voltage at lower pressure leads to more
energetic ion bombardment to help the etch reactions to overcome
activation energy barrier. Second, lower pressure leads to faster
desorption and diffusion of reaction byproducts. Higher V.sub.bias
also enhances physical sputtering by energetic ions. To delineate
the contributions from reactive ion etching and physical
sputtering, we conducted comparison runs using pure argon plasma.
The results are listed in Table 26 below.
26TABLE 26 Argon plasma etching of Al.sub.2O.sub.3 Power density
Pressure Al.sub.2O.sub.3 etch rate V.sub.bias Power (W)
(W/cm.sup.2) (mTorr) (nm/min) (V) 200 1.10 5 0.6 173 200 1.10 50
1.0 189 200 1.10 500 -0.4 185
[0087] The data showed pure argon plasma essentially did not etch
Al.sub.2O.sub.3 even with very high power and a relatively higher
V.sub.bias than that of BCl.sub.3 plasmas. This indicates that
physical sputtering may not be the primary mechanism to etch
Al.sub.2O.sub.3. Instead, ion bombardment enhanced chemical
etching, or reactive ion etching (RIE) may be the primary
mechanism.
[0088] Tables 24 and 25 showed higher power and lower pressure can
increase V.sub.dc, which in turn enhances chemical etching of
high-k materials. One can also operate the RF plasma at lower
frequencies. Ions transiting through a plasma sheath often exhibit
a bi-modal energy distribution at lower frequencies. Bimodal ion
energy distribution results in a large fraction of the ions
impinging onto reactor surfaces with higher energies. This can be
an effective strategy to enhance plasma cleaning of high-k
deposition residues from grounded ALD chamber surfaces. At a fixed
RF excitation frequency (such as 13.56 MHz), the data in Tables 24
and 25 show higher power and lower pressure can increase bias
voltage, which in turn enhances chemical etching of high-k
materials. Lower pressure and higher power is particularly
effective to enhance plasma etching of substrates coated with
high-k films. For ALD chamber cleaning, one must balance the
requirements between RF powered reactor components and grounded
reactor components (such as chamber walls).
Example 2
[0089] Plasma Etching/Cleaning of HfO.sub.2 Samples
[0090] At 500 mTorr pressure, etching of HfO.sub.2 was achieved at
all power levels between 50 and 200 W. The results are listed in
Table 27 below.
27TABLE 27 BCl.sub.3 plasma etching of HfO.sub.2 Power density
Pressure HfO.sub.2 etch rate V.sub.bias Power (W) (W/cm.sup.2)
(mTorr) (nm/min) (V) 50 0.27 500 1.6 14 50 0.27 500 1.4 16 100 0.55
500 4.7 34 200 1.10 500 14.7 63
Example 3
[0091] Plasma Etching/Cleaning of ZrO.sub.2 Samples
[0092] Several experiments were conducted with ZrO.sub.2 samples
using 500 mTorr pressure and various power levels between 50 and
200 W. The results are listed in Table 28 below.
28TABLE 28 BCl.sub.3 plasma etching of HfO.sub.2 Power density
Pressure ZrO.sub.2 etch rate V.sub.bias Power (W) (W/cm.sup.2)
(mTorr) (nm/min) (V) 50 0.27 500 0.3 16 100 0.55 500 -3.8* 32 100
0.55 500 -2.5* 45 200 1.10 500 7.1 65 *The film became thicker
after one minute exposure to the plasma.
[0093] FIG. 3 shows the relative comparison of BCl.sub.3 plasma
etch rates of high-k materials HfO.sub.2, Al.sub.2O.sub.3, and
ZrO.sub.2 at 500 mTorr chamber pressure and 1 W/cm.sup.2 RF power
density. It can be seen that HfO.sub.2 has the highest etch rate,
and ZrO.sub.2 has the lowest etch rate among the three high-k
materials.
[0094] Examples 4 and 5 illustrate BCl3 thermal etching/cleaning of
high-k materials. FIG. 4 is a schematic of the experimental setup
for examples 4 and 5. In this reactor RF power can be applied on
the top electrode, and the lower electrode and the chamber walls
are grounded. This reactor can be operated with both RF plasma and
thermal heating during an etching/cleaning experiments. Only
thermal heating was used in examples 4 and 5. The lower
electrode/pedestal can be heated by an AC powered heater and
controlled by the temperature controller. The temperature range of
the lower electrode/pedestal is from room temperature up to
700.degree. C. The sample and the carrier wafer were placed on the
lower electrode/pedestal. Sample surface temperature is about
50.degree. C. lower than the lower electrode set point in ambient
atmosphere. Sample preparation and measurement procedures were
similar to those in examples 1 through3. After sample introduction,
the reactor was evacuated, and the heater was turned out. When the
lower electrode reached the set point, process gases were
introduced into the chamber to reach a set pressure. The sample was
exposed to the process gases for a set period of time. The process
gases were evacuated and the sample was retrieved from the chamber
for measurement.
Example 4
[0095] Thermal Etching/Cleaning of Al.sub.2O.sub.3 Samples
[0096] Several experiments were conducted using BCl.sub.3 as the
etchant for thermal etching/cleaning of Al.sub.2O.sub.3 samples.
The process variables were lower electrode temperature, chamber
pressure, and BCl.sub.3 flow rate. The results are listed in Table
29.
29TABLE 29 BCl.sub.3 thermal etching of Al.sub.2O.sub.3 Lower
Electrode Set Chamber Pressure BCl.sub.3 Flow Rate Etch Rate
Temperature (.degree. C.) (Torr) (sccm) (nm/min) 200 100 100 0.0
350 25 100 0.1 350 100 100 0.2 350 100 100 0.2 350 100 0 0.3 350
200 100 0.3 350 400 100 0.7 600 100 100 0.6
Example 5
[0097] Thermal Etching/Cleaning of HfO.sub.2 Samples
[0098] A similar set of experiments were conducted using BCl.sub.3
as the etchant for thermal etching/cleaning of HfO.sub.2 samples.
The process variables were lower electrode temperature, chamber
pressure, and BCl.sub.3 flow rate. The results are listed in Table
30.
30TABLE 30 BCl.sub.3 thermal etching of HfO.sub.2 Lower Electrode
Set Chamber Pressure BCl.sub.3 Flow Rate Etch Rate Temperature
(.degree. C.) (Torr) (sccm) (nm/min) 200 100 100 0.0 350 25 100 0.1
350 100 100 0.6 350 100 100 0.6 350 100 0 0.6 350 200 100 1.1 350
400 100 2.4 600 100 100 1.1
[0099] FIG. 5 examines the etch rate dependence on lower electrode
temperature at constant chamber pressure and BCl.sub.3 flow rate.
It can be seen that both Al.sub.2O.sub.3 and HfO.sub.2 etch rates
increase at temperature increases. The etch rates of HfO.sub.2 are
higher than those of Al.sub.2O.sub.3 under the same conditions.
[0100] FIG. 6 examines the etch rate dependence on chamber pressure
at constant lower electrode set temperature and BCl.sub.3 flow
rate. It can be seen that etch rates increase at higher pressures.
At lower electrode temperature about 350.degree. C., increasing
chamber pressure is a more effective method to enhance etch rates.
Again, the etch rates of HfO.sub.2 are higher than those of
Al.sub.2O.sub.3 under the same conditions.
[0101] The data in Tables 29 and 30 shows that there is no strong
dependence between etch rate and BCl.sub.3 flow rate. This means
one can operate thermal etching/cleaning either with continuous
flow of etchant gases (such as BCl.sub.3) or with static chamber at
a set pressure without flow.
[0102] While the invention has been described in detail and with
reference to specific examples thereof, it will be apparent to one
skilled in the art that various changes and modifications can be
made therein without departing from the spirit and scope
thereof.
* * * * *