U.S. patent application number 16/442930 was filed with the patent office on 2019-11-07 for organometallic compounds and methods for the deposition of high purity tin oxide.
This patent application is currently assigned to SEASTAR CHEMICALS INC.. The applicant listed for this patent is SEASTAR CHEMICALS INC.. Invention is credited to Cunhai DONG, Diana FABULYAK, Wesley GRAFF, Rajesh ODEDRA.
Application Number | 20190337969 16/442930 |
Document ID | / |
Family ID | 65229074 |
Filed Date | 2019-11-07 |
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United States Patent
Application |
20190337969 |
Kind Code |
A1 |
ODEDRA; Rajesh ; et
al. |
November 7, 2019 |
ORGANOMETALLIC COMPOUNDS AND METHODS FOR THE DEPOSITION OF HIGH
PURITY TIN OXIDE
Abstract
Disclosed herein are compounds useful for the deposition of high
purity tin oxide. Also disclose are methods for the deposition of
tin oxide films using such compounds. Such films demonstrate high
conformality, high etch selectivity and are optically transparent.
Such compounds are those of the Formula as follows
R.sub.x--Sn-A.sub.4-x wherein: A is selected from the group
consisting of (Y.sub.aR'.sub.z) and a 3- to 7-membered N-containing
heterocyclic group; each R group is independently selected from the
group consisting of an alkyl or aryl group having from 1 to 10
carbon atoms; each R' group is independently selected from the
group consisting of an alkyl, acyl or aryl group having from 1 to
10 carbon atoms; x is an integer from 0 to 4; a is an integer from
0 to 1; Y is selected from the group consisting of N, O, S, and P;
and z is 1 when Y is O, S or when Y is absent and z is 2 when Y is
N or P.
Inventors: |
ODEDRA; Rajesh; (Victoria,
CA) ; DONG; Cunhai; (Victoria, CA) ; FABULYAK;
Diana; (Victoria, CA) ; GRAFF; Wesley;
(Singapore, SG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEASTAR CHEMICALS INC. |
Sidney |
|
CA |
|
|
Assignee: |
SEASTAR CHEMICALS INC.
Sidney
CA
|
Family ID: |
65229074 |
Appl. No.: |
16/442930 |
Filed: |
June 17, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/CA2018/050933 |
Jul 31, 2018 |
|
|
|
16442930 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03F 7/161 20130101;
C23C 16/45536 20130101; C23C 16/505 20130101; C23C 16/45553
20130101; G03F 7/09 20130101; C07F 7/2284 20130101; G03F 7/167
20130101; C23C 16/407 20130101 |
International
Class: |
C07F 7/22 20060101
C07F007/22; G03F 7/16 20060101 G03F007/16; G03F 7/09 20060101
G03F007/09 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 2, 2017 |
CA |
2975104 |
Claims
1. An organometallic compound of Formula 1: R.sub.x--Sn-A.sub.4-x
Formula I wherein: A is selected from the group consisting of
(Y.sub.aR'.sub.z) and a saturated 3- to 7-membered N-containing
heterocyclic group; each R group is independently selected from the
group consisting of an alkyl or aryl group having from 1 to 10
carbon atoms; each R' group is independently selected from the
group consisting of an alkyl, acyl or aryl group having from 1 to
10 carbon atoms; x is an integer from 0 to 4; a is an integer from
0 to 1; Y is selected from the group consisting of N, O, and P; and
z is 1 when Y is O or when Y is absent and z is 2 when Y is N or P,
wherein when Y is N, R' represents a combination of two different
alkyl, acyl, or aryl groups, and wherein when Y is O, x is 2.
2. The organometallic compound of claim 1, wherein A is selected
from the group consisting of an (NR'.sub.2) group and a saturated
3- to 7-membered N-containing heterocyclic group.
3. The organometallic compound of claim 2, wherein A is an
(NR'.sub.2) group.
4. The organometallic compound of claim 2, wherein A is a saturated
3- to 7-membered N-containing heterocyclic group.
5. The organometallic compound of claim 4, wherein A is a
pyrrolidinyl group.
6. The organometallic compound of claim 1, wherein A.sub.4-x is
(NEtMe).sub.2.
7. The organometallic compound of claim 1, wherein each R and R'
group is an independently selected alkyl group having from 1 to 10
carbon atoms.
8. The organometallic compound of claim 7, wherein each R and R'
group is an independently selected alkyl group having from 1 to 6
carbon atoms.
9. The organometallic compound of claim 8, wherein each R and R'
group is an independently selected alkyl group having from 1 to 4
carbon atoms.
10. The organometallic compound of claim 1, wherein each R and R'
is independently selected from the group consisting of methyl,
ethyl, propyl, iso-propyl, tert-butyl, iso-butyl and n-butyl.
11. The organometallic compound of claim 1, wherein R and R'
represent different alkyl groups.
12. The organometallic compound of claim 1, wherein the compound of
Formula I is selected from the group consisting of
Me.sub.2Sn(NEtMe).sub.2, t-BuSn(NEtMe).sub.3, i-PrSn(NEtMe).sub.3,
n-PrSn(NEtMe).sub.3, EtSn(NEtMe).sub.3, i-BuSn(NEtMe).sub.3,
Et.sub.2Sn(NEtMe).sub.2, Me.sub.2Sn(NEtMe).sub.2, Sn(NEtMe).sub.4,
Bu.sub.2Sn(NEtMe).sub.2, Sn(Pyrrolidinyl).sub.4 and
Bu.sub.2Sn(Pyrrolidinyl).sub.2.
13. The organometallic compound of claim 12, wherein the compound
of Formula I is selected from the group consisting of
Me.sub.2Sn(NEtMe).sub.2, Sn(Pyrrolidinyl).sub.4; and
Bu.sub.2Sn(Pyrrolidinyl).sub.2.
14. The organometallic compound of claim 13, wherein the compound
of Formula I is Me.sub.2Sn(NEtMe).sub.2.
15. A composition comprising a combination of at least two
organometallic compounds, wherein each of the organometallic
compounds is represented by Formula I: R.sub.x--Sn-A.sub.4-x
Formula I wherein: A is selected from the group consisting
of(Y.sub.aR'.sub.2) and a3- to 7-membered N-containing heterocyclic
group; each R group is independently selected from the group
consisting of an alkyl or aryl group having from 1 to 10 carbon
atoms; each R' group is independently selected from the group
consisting of an alkyl, acyl or aryl group having from 1 to 10
carbon atoms; x is an integer from 0 to 4; a is an integer from 0
to 1; Y is selected from the group consisting of N, O, and P; and z
is 1 when Y is O or when Y is absent and z is 2 when Y is N or P,
wherein at least one of the organometallic compounds is a compound
represented by Formula I in which: Y is N, a is 1, and x is 2; or Y
is N, a is 1, and R' represents a combination of two different
alkyl, acyl, or aryl groups.
16. The composition of claim 15, wherein at least one of the
organometallic compounds is selected from the group consisting of
MeSn(NMe.sub.2).sub.3 and Sn(NMe.sub.2).sub.4.
17. A method for the deposition of a tin oxide layer on a substrate
by a vapour deposition process, the method comprising the steps of:
a. providing at least one substrate having functional O--H groups
covering the surface; b. delivering to said substrate an
organometallic compound in the gaseous phase; c. delivering to said
substrate an oxygen source in the gaseous phase; d. activating the
gaseous phase to form the tin oxide layer; and e. repeating steps a
to d to generate the desired thickness of the tin oxide layer,
wherein the organometallic compound is of Formula I:
R.sub.x--Sn-A.sub.4-x Formula I wherein: A is selected from the
group consisting of (YaR'z) and a 3- to 7-membered N-containing
heterocyclic group; each R group is independently selected from the
group consisting of an alkyl or aryl group having from 1 to 10
carbon atoms; each R' group is independently selected from the
group consisting of an alkyl, acyl or aryl group having from 1 to
10 carbon atoms; x is an integer from 0 to 4; a is an integer from
0 to 1; Y is selected from the group consisting of N, O, S, and P;
and z is 1 when Y is O, S or when Y is absent and z is 2 when Y is
N or P.
18. The method of claim 17, wherein the activation condition is
plasma generation.
19. A method for spacer-defined double patterning deposition, the
method comprising the steps of: (a) depositing a layer of
(photo)resist onto a substrate having functional O--H groups
covering the surface, forming a pattern in the resist with
electron-beam (e-beam) lithography, and developing the photoresist
to give the pattern; (b) depositing a spacer layer onto the resist
using energy-enhanced ALD in the presence of an organometallic
compound; (c) performing an anisotropic etch to remove the tops of
the features, using reactive ion etching (RIE) or ion milling (IM);
(d) removing the photoresist, either by a wet or plasma etch; (e)
anisotropically etching into the target layer; and (f) removing the
spacer, leaving the patterned substrate, wherein the organometallic
compound is of Formula I: Rx-Sn-A.sub.4-x Formula I wherein: A is
selected from the group consisting of (Y.sub.aR'.sub.z) and a 3- to
7-membered N-containing heterocyclic group; each R group is
independently selected from the group consisting of an alkyl or
aryl group having from 1 to 10 carbon atoms; each R' group is
independently selected from the group consisting of an alkyl, acyl
or aryl group having from 1 to 10 carbon atoms; x is an integer
from 0 to 4; a is an integer from 0 to 1; Y is selected from the
group consisting of N, O, S, and P; and z is 1 when Y is O, S or
when Y is absent and z is 2 when Y is N or P.
20. A method of using multistage distillation to purify the
organometallic compound of claim 1.
21. The method of claim 19, wherein 2 to 20 stages are required to
reduce metal contamination to <1 ppm.
22. The method of claim 19, wherein 2 to 20 stages are required to
reduce metal contamination to <100 ppb.
23. The method of claim 19, wherein 2 to 20 stages are required to
reduce metal contamination to <10 ppb.
24. The method of claim 19, wherein 2 to 20 stages are required to
reduce metal contamination to 1 ppb or less.
Description
TECHNICAL FIELD
[0001] The disclosure relates to organometallic compounds useful
for the deposition of high purity tin oxide and to the purification
of such organometallic compounds. Also disclosed are methods for
the deposition of high purity tin oxide films using such
compounds.
BACKGROUND
[0002] The semiconductor industry is producing more and more
components having smaller and smaller feature sizes. The production
of such semiconductor devices reveals new design and manufacturing
challenges which must be addressed in order to maintain or improve
semiconductor device performance (for example, the conductor line
width and spacing within the semiconductor devices decreases). The
production of semiconductor wiring stacks with high density, high
yield, good signal integrity as well as suitable power delivery
also presents challenges.
[0003] Lithography is a critical pattern transfer technique widely
used in the fabrication of a variety of electronic devices which
contain microstructures, such as semiconductor devices and liquid
crystal devices. As device structures are miniaturized, masking
patterns used in the lithography process must be optimized to
accurately transfer patterns to the underlying layers.
[0004] Multiple-pattern lithography represents a class of
technologies developed for photolithography in order to enhance the
feature density of semiconductor devices. Double-patterning, a
subset of multiple-patterning, employs multiple masks and
photolithographic steps to create a particular level of a
semiconductor device. With benefits such as tighter pitches and
narrower wires, double-patterning alters relationships between
variables related to semiconductor device wiring and wire quality
to sustain performance.
[0005] Recently, a liquid immersion lithography method has been
reported, which purports to address some of the issues facing the
industry. In this method, a resist film is exposed through a liquid
refractive index medium (refractive index liquid, immersion liquid)
such as pure water or a fluorocarbon inert liquid, having a
predetermined thickness, with the liquid refractive index medium
lying at least on the resist film between a lens and the resist
film on a substrate. In this method, the space of the path of
exposure light, which has conventionally been filled with an inert
gas, such as air or nitrogen gas, is replaced by a liquid having a
larger refractive index (n), for example, pure water, with the
result that even though a light source having a wavelength for the
exposure conventionally used is employed, high resolution can be
achieved without lowering the depth of focus, like the case where a
light source having a shorter wavelength or a lens having a higher
NA (numerical aperture) is used.
[0006] By employing liquid immersion lithography, a resist pattern
having a higher resolution and an excellent depth of focus can be
formed at a low cost, using a lens mounted on existing exposure
systems (i.e. the purchase of a new exposure system is not
necessary), such that the liquid immersion lithography has
attracted considerable attention.
[0007] As a result of moving to immersion lithography and
multi-patterning, the need exists for a new class of conformally
deposited materials to be deposited on top of photo resist, BARC,
and other traditional masking layers. This new conformal deposition
layer can server 2 major functions: [0008] 1) It can act as a
transparent protection layer (or "mask") to prevent chemical attack
by the immersion lithography fluid. In this case, the conformal
layer needs to be transparent, and be able to integrate with the
lithography process without adverse patterning and exposure issues.
[0009] 2) It can have a higher etch selectivity than prior art and
traditional films such as amorphous carbon (which become more
opaque with increasing thickness). For example, multi-patterning
processes may require thicker (>10,000 A), and therefore more
opaque, amorphous carbon layers in order to achieve the necessary
etch protection. To achieve a similar etch resistance, metal oxide
conformal films can remain transparent while maintaining the
required etch selectivity during the plasma etch process.
[0010] High purity of the reactant gases used in these processes
are required, in order to ensure consistent chemical makeup for
smoothness, etch and deposition characteristics, 100% step
coverage/conformality requirement, and low radiation emissions
known to damage electrical devices during fabrication or throughout
the lifetime of the electrical device.
[0011] The purity of the film produced is also required to be high,
due to the use of the film as a resist protection layer during etch
or during litho immersion processing. Impurities in the film can
have adverse reactions, chemically or optically, which interfere
with the pattern quality and which can affect critical dimensions
on the device features, resulting in degradation of the integrated
device performance.
[0012] Conventional resist compositions cannot always be used in
liquid immersion lithography processes, for a variety of reasons.
For example, in the liquid immersion lithography process, the
resist film is directly in contact with the refractive index liquid
(immersion liquid) during the exposure, and hence the resist film
is vulnerable to attack by the liquid. Resist compositions suitable
for use in liquid immersion lithography processes must also be
transparent to the exposure light. Further, conventional resist
compositions may not be able to achieve a satisfactory resolution
of pattern in liquid immersion lithography due to a change in their
properties by the liquid, despite their utility in lithography
employing the exposure through a layer of air.
[0013] Thus, there remains a need for improved transparent resist
protection layers which can meet the increased requirements of the
industry. Further, higher selectivity ALD films are needed for
multi-patterning, as outlined above.
SUMMARY
[0014] Disclosed herein are compounds useful for the deposition of
high purity tin oxide. Also disclosed are methods for the
deposition of tin oxide films using such compounds. Such films
demonstrate high conformality, high etch selectivity, high hardness
and modulus, and are optically transparent.
[0015] Compounds include those of Formula I, below:
R.sub.x--Sn-A.sub.4-x Formula I
wherein: [0016] A is selected from the group consisting of
(Y.sub.aR'.sub.z) and a 3- to 7-membered N-containing heterocyclic
group; [0017] each R group is independently selected from the group
consisting of an alkyl or aryl group having from 1 to 10 carbon
atoms; [0018] each R' group is independently selected from the
group consisting of an alkyl, acyl or aryl group having from 1 to
10 carbon atoms; [0019] x is an integer from 0 to 4; [0020] a is an
integer from 0 to 1; [0021] Y is selected from the group consisting
of N, O, S, and P; and [0022] z is 1 when Y is O, S or when Y is
absent and z is 2 when Y is N or P
[0023] Also disclosed is the deposition of tin oxide using such
compounds. The use of compounds of Formula I in the methods
disclosed herein allows for chemical vapour deposition (CVD) and
atomic layer deposition (ALD) of tin oxide at a low temperature,
and produces films consisting of high purity tin oxide having low
metallic impurities, low alpha emission characteristics, high
hardness and modulus, and >99% step coverage (i.e. high
conformality) over device features and topography.
[0024] Also disclosed is the purification of compounds of Formula I
by multistage distillation. Such purification yields so-called
"ultra-pure" compounds having much lower levels of metallic
impurities compared to compounds purified by conventional means.
The use of such ultra-pure compounds in the processes disclosed
herein results in films having improved properties compared to
those known in the art. For example, the films may have improved
hermetic properties, low metallic impurities and improvements in
the associated yield loss and long term reliability failures
resulting from such metallic impurities. Multistage distillation
may be carried out in the form of packed columns, stage
distillation columns employing trays, multiple distillation
columns, or other types of multistage distillation.
[0025] The tin oxide film so produced may also exhibit high etch
selectivity verses traditional masking and conformal layers used in
multilayer patterning integration techniques, resulting in a
thinner film requirement as compared to traditional films such as
amorphous carbon, boron doped carbon, etc.
[0026] In an embodiment, in the organometallic compound of Formula
I, A is selected from the group consisting of an (NR'.sub.2) group
and a 3- to 7-membered N-containing heterocyclic group. In an
embodiment, A is an (NR'.sub.2) group. In an embodiment, A is a 3-
to 7-membered N-containing heterocyclic group. In an embodiment, A
is a pyrrolidinyl group. In an embodiment, A.sub.4-x is
(NMe.sub.2).sub.2 or (NEtMe).sub.2.
[0027] In other embodiments R and R' group is an independently
selected alkyl group having from 1 to 10 carbon atoms. It is
contemplated that each R and R' group may be an independently
selected alkyl group having from 1 to 6 carbon atoms. In
embodiments, each R and R' group is an independently selected alkyl
group having from 1 to 4 carbon atoms. In embodiments, R and R' is
independently selected from the group consisting of methyl, ethyl,
propyl, iso-propyl, tert-butyl, iso-butyl and n-butyl. In
embodiments R and R' represent different alkyl groups.
[0028] In an embodiment, the compound of Formula I is selected from
the group consisting of Me.sub.2Sn(NMe.sub.2).sub.2,
Me.sub.2Sn(NEtMe).sub.2, t-BuSn(NEtMe).sub.3, i-PrSn(NEtMe).sub.3,
n-Pr(NEtMe).sub.3, EtSN(NEtMe).sub.3, i-BuSn(NEtMe).sub.3,
Et.sub.2Sn(NEtMe).sub.2, Me.sub.2Sn(NEtMe).sub.2, Sn(NEtMe).sub.4,
Bu.sub.2Sn(NEtMe).sub.2, Et.sub.2Sn(NMe.sub.2).sub.2,
Me.sub.2Sn(NEt.sub.2).sub.2, Sn(Pyrrolidinyl).sub.4 and
Bu.sub.2Sn(Pyrrolidinyl).sub.2.
[0029] In embodiments, the compound of Formula I is selected from
the group consisting of Me.sub.2Sn(NMe.sub.2).sub.2,
Me.sub.2Sn(NEtMe).sub.2, Et.sub.2Sn(NMe.sub.2).sub.2,
Me.sub.2Sn(NEt.sub.2).sub.2, Sn(Pyrrolidinyl).sub.4; and
Bu.sub.2Sn(Pyrrolidinyl).sub.2.
[0030] In embodiments, the compound of Formula I is selected from
the group consisting of Me.sub.2Sn(NEtMe).sub.2 and
Me.sub.2Sn(NMe.sub.2).sub.2.
[0031] In embodiments, the compound of Formula I is
Me.sub.2Sn(NMe.sub.2).sub.2.
[0032] In embodiments, a composition is provided that comprises the
organometallic compound of any of the disclosed compounds and
another organometallic compound containing Sn. The another
organometallic compound may be a compound of Formula I.
[0033] In various embodiments, another organometallic compound is
selected from the group consisting of MeSn(NMe.sub.2).sub.3 and
Sn(NMe.sub.2).sub.4.
[0034] A method id disclosed for the deposition of a tin oxide
layer on a substrate by a vapour deposition process. The method
comprises the steps of: [0035] (a) providing at least one substrate
having functional O--H groups covering the surface; [0036] (b)
delivering to said substrate the organometallic compound of any of
claim 1-6, 8-10, or 12-15 in the gaseous phase; [0037] (c)
delivering to said substrate an oxygen source in the gaseous phase,
forming the tin oxide layer; and [0038] (d) repeating steps a to c
to generate the desired thickness of the tin oxide layer, [0039]
(e) wherein steps b and c are carried out under activating
conditions.
[0040] In certain embodiments, the activation condition is plasma
generation.
[0041] A method is also disclosed for spacer-defined double
patterning deposition. The method comprises the steps of: [0042]
(a) depositing a layer of (photo)resist onto a substrate having
functional O--H groups covering the surface, forming a pattern in
the resist with electron-beam (e-beam) lithography, and developing
the photoresist to give the pattern; [0043] (b) depositing a spacer
layer onto the resist using energy-enhanced ALD in the presence of
the organometallic compound of any one of claim 1-6, 8-10, or
12-15; [0044] (c) performing an anisotropic etch to remove the tops
of the features, using reactive ion etching (RIE) or ion milling
(IM); [0045] (d) removing the photoresist, either by a wet or
plasma etch; [0046] (e) anisotropically etching into the target
layer; and [0047] (f) removing the spacer, leaving the patterned
substrate.
[0048] In an embodiment, a method of using multistage distillation
to purify the organometallic compounds disclosed. In an embodiment,
2 to 20 stages are required to reduce metal contamination to <1
ppm. In an embodiment, 2 to 20 stages are required to reduce metal
contamination to <100 ppb. In an embodiment, 2 to 20 stages are
required to reduce metal contamination to <10 ppb. In an
embodiment, 2 to 20 stages are required to reduce metal
contamination to 1 ppb or less.
[0049] The foregoing and other features of the invention and
advantages of the present invention will become more apparent in
light of the following detailed description of the preferred
embodiments, as illustrated in the accompanying figures. As will be
realized, the invention is capable of modifications in various
respects, all without departing from the invention. Accordingly,
the drawings and the description are to be regarded as illustrative
in nature, and not as restrictive
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] FIG. 1 shows a sectional view of one embodiment of a
processing chamber useful for the processes disclosed herein.
[0051] FIGS. 2A-2E illustrate schematically cross-sectional views
of a substrate at different stages of an integrated circuit
fabrication sequence.
[0052] FIG. 3 is a process flow diagram depicting a method for
depositing a tin oxide film
[0053] FIG. 4 is a schematic representation of a spacer-defined
double-patterning technique.
[0054] FIG. 5 shows the NMR spectrum of Me.sub.3SnNMe.sub.2.
[0055] FIG. 6 shows the NMR spectrum of Sn(NMe.sub.2).sub.4.
[0056] FIG. 7 shows the NMR spectrum of
Me.sub.2Sn(NEtMe).sub.2.
[0057] FIG. 8 shows the NMR spectrum of
Bu.sub.2Sn(NMe.sub.2).sub.2.
[0058] FIG. 9 shows the NMR spectrum of Me.sub.2SnEt.sub.2.
[0059] FIG. 10 shows the NMR spectrum of Me.sub.4Sn.
[0060] FIG. 11 shows the NMR spectrum of Bu.sub.2Sn(OMe).sub.2.
[0061] FIG. 12 shows the NMR spectrum of Bu.sub.2Sn(OAc).sub.2.
[0062] FIG. 13 shows the NMR spectrum of
Et.sub.2Sn(NMe.sub.2).sub.2.
[0063] FIG. 14 shows the NMR spectrum of
Me.sub.2Sn(NEt.sub.2).sub.2.
[0064] FIG. 15 shows the NMR spectrum of
Sn(Pyrrolodinyl).sub.4.
[0065] FIG. 16 shows the NMR spectrum of
Bu.sub.2Sn(Pyrrolodinyl).sub.2.
[0066] FIG. 17 shows the NMR spectrum of
Et.sub.2Sn(Pyrrolodinyl).sub.2.
[0067] FIG. 18 shows the NMR spectrum of
Me.sub.2Sn(NMe.sub.2).sub.2.
[0068] FIG. 19 shows the NMR spectrum of tBuSn(NMe.sub.2).sub.3
[0069] FIG. 20 shows the NMR of the reaction of (NMe.sub.2).sub.4Sn
with ethanol.
[0070] FIG. 21 shows the NMR of the reaction of Me.sub.3SnNMe.sub.2
with water.
[0071] FIG. 22 shows the NMR of the reaction of
Bu.sub.2Sn(OAc).sub.2 with methanol.
[0072] FIG. 23 shows the NMR of the reaction of
Bu.sub.2Sn(OMe).sub.2 with acetic acid.
[0073] FIG. 24 shows the NMR of the reaction of
Bu.sub.2Sn(NMe.sub.2).sub.2 with methanol.
[0074] FIG. 25 shows the NMR of Me.sub.4Sn before and after heating
at 200.degree. C.
[0075] FIG. 26 shows the NMR of Et.sub.2Sn(NMe.sub.2).sub.2 before
and after heating at 200.degree. C.
[0076] FIG. 27 shows the NMR of Me.sub.2Sn(NMe.sub.2).sub.2 before
and after heating at 150.degree. C.
[0077] FIG. 28 shows the decomposition temperatures of illustrative
compounds of Formula I.
[0078] FIG. 29 shows a schematic of a multistage distillation
apparatus.
DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS
[0079] Disclosed are organometallic compounds of Formula I,
below:
R.sub.x--Sn-A.sub.4-x Formula I
wherein: [0080] A is selected from the group consisting of
(Y.sub.aR'.sub.z) and a 3- to 7-membered N-containing heterocyclic
group; [0081] each R group is independently selected from the group
consisting of an alkyl or aryl group having from 1 to 10 carbon
atoms; [0082] each R' group is independently selected from the
group consisting of an alkyl, acyl or aryl group having from 1 to
10 carbon atoms; [0083] x is an integer from 0 to 4; [0084] a is an
integer from 0 to 1; [0085] Y is selected from the group consisting
of N, O, S, and P; and [0086] z is 1 when Y is O, S or when Y is
absent and z is 2 when Y is N or P
[0087] Compounds of Formula I include those in which R is selected
from the group consisting of alkyl and aryl groups having from 1 to
10 carbon atoms. Particular compounds are those in which R is
selected from the group consisting of alkyl and aryl groups having
from 1 to 6 carbon atoms. More particular are those in which R is
selected from the group consisting of alkyl and aryl groups having
from 1 to 4 carbon atoms. Examples of such compounds include those
in which R is a methyl, ethyl or a butyl group.
[0088] Compounds of Formula I include those in which R' is selected
from the group consisting of alkyl, acyl and aryl groups having
from 1 to 10 carbon atoms. Particular compounds are those in which
R' is selected from the group consisting of alkyl, acyl and aryl
groups having from 1 to 6 carbon atoms. More particular are those
in which R' is selected from the group consisting of alkyl, acyl
and aryl groups having from 1 to 4 carbon atoms. Examples of such
compounds include those in which R' is a methyl group, an ethyl
group or an acetyl group.
[0089] Compounds of Formula I include those in which Y is selected
from the group consisting of N, O, S, and P. Particular compounds
are those in which Y is selected from the group consisting of N and
O.
[0090] Compounds of Formula I include those in which x is an
integer from 0 to 4. In particular embodiments, x is an integer
from 1 to 3. More preferably, x is 2.
[0091] Compounds of Formula I include those in which A is a 3- to
7-membered N-containing heterocyclic group such as aziridinyl,
pyrrolidinyl, and piperidinyl. Particular compounds are those in
which A is a pyrrolidinyl or piperidinyl group.
[0092] Compounds of Formula I include those in which R is an alkyl
group and A is an NR'.sub.2 group, and wherein R' is an alkyl
group. Particular compounds are those in which R and R' represent
different alkyl groups.
[0093] Compounds of Formula I are thermally stable whilst
exhibiting good reactivity. Thus, delivery of the compound to the
deposition chamber will take place without decomposition occurring.
(decomposition results in a deposited film which will not be
uniform). A good stability and reactivity profile, as demonstrated
by the compounds of the invention, also means that less material is
required to be delivered to the growth chamber (less material is
more economic), and cycling will be faster (as there will be less
material left in the chamber at the end of the process to be pumped
off), meaning that thicker films can be deposited in shorter times,
so increasing throughput. Further, ALD can be carried out at much
lower temperatures (or using a wider temperature window) using
compounds of Formula I than processes of the art. Thermal stability
also means that material can be purified much more easily after
synthesis, and handling becomes easier.
[0094] Such compounds are useful for encapsulating and protecting
the resist layers used in liquid immersion lithography (i.e. acting
as a "mask"). Thus, the compounds disclosed herein may be used for
the manufacture of a transparent tin oxide film having properties
suitable for deposition over photoresists, or other organic masking
layers, to allow for protection of the underlying layer during
liquid immersion lithography, and which permits the manufacture of
devices having improved semiconductor device performance such as
low defect density, improved device reliability, high device
density, high yield, good signal integrity and suitable power
delivery, as required by the industry.
[0095] Further, the use of a compound of Formula I in the methods
disclosed herein allows for chemical vapour deposition (CVD) and
atomic layer deposition (ALD) of tin oxide at a low temperature,
and produces films consisting of high purity tin oxide having low
metallic impurities, low alpha emission characteristics, and
>99% step coverage (i.e. high comformality) over device features
and topography.
[0096] FIG. 1 shows a sectional view of one embodiment of a
processing chamber 800 suitable for CVD (Chemical Vapor
Deposition), ALD (Atomic Layer Deposition), Etching, or doping
dopants into a substrate. Suitable processing chambers that may be
adapted for use with the teachings disclosed herein include those
commonly used in integrated circuit fabrication, it is contemplated
that many types of processing chambers may be adapted to benefit
from one or more of the inventive features disclosed herein. The
processing chamber 800 as described herein may be utilized as a
plasma deposition apparatus. However, the processing chamber 800
may also include, but not be limited to, deposition, etching, and
doping systems. The processing could be using either thermal or
plasma deposition or etching mechanisms. Furthermore, the
deposition apparatus can deposit or etch many differing materials
on a substrate. One such process includes deposition of a conformal
tin oxide on a substrate, such as a semiconductor substrate, with
desired physical properties of film transparency to varying
wavelengths of light, deposition conformality, tin oxide low in
metal impurities, low film roughness, and high etch selectivity to
underlying layers.
[0097] The processing chamber 800 may include chamber body 801
defining an interior processing region 809. A substrate support 834
is disposed in the processing chamber 800. A substrate 838 having
features 844 formed thereon may be disposed on the substrate
support 834 during a directional plasma process. The substrate 838
may include, but not be limited to, a semiconductor wafer, flat
panel, solar panel, and polymer substrate. The semiconductor wafer
may have a disk shape with a diameter of 200 millimeters (mm), 300
millimeters (mm) or 450 millimeters (mm) or other size, as
needed.
[0098] A RF plasma source 806 is coupled to the chamber body 801
and configured to generate a plasma 840 in the processing chamber
800.
[0099] A gas source 888 is coupled to the processing chamber 800 to
supply a gas to the interior processing region 809. Examples of a
gas include, but are not limited to, oxidants such as O.sub.2,
O.sub.3, NO, NO2, CO2, H2O2, and H2O. The plasma source 806 may
generate the plasma 840 by exciting and ionizing the gas provided
to the processing chamber 800. Ions in the plasma 840 may be
attracted across the plasma sheath 842 by different mechanisms. A
bias source 890 is coupled to the substrate support 834 configured
to bias the substrate 838 to attract ions 802 from the plasma 840
across the plasma sheath 842. The bias source 890 may be a DC power
supply to provide a DC voltage bias signal or an RF power supply to
provide an RF bias signal.
[0100] In operation, a feed gas comprising a compound of Formula I
may be flowed in step 1 to saturate the surface of features 844,
then in subsequent step 2 an oxidizing gas, as described above, is
ionized in the plasma and reacts on surface 844 to form a 0.1 to
2.0 A conformal layer of SnO.sub.2 or other layers (layer 847).
Then steps 1 and 2 are repeated until the desired conformal film
thickness is achieved. In the case of an etching reaction, the
process steps and gas flows would be designed to modify the
chemical make-up of layer 844 in step 1 and followed by the gas in
step 2 to etch a thin layer of the modified 844 surface. Once
again, steps 1 and 2 would be repeated to achieve the desired etch
target removal of layer 844.
[0101] In an additional embodiment, layer 844 could be comprised of
organic material such as photo resist that is sensitive to
immersion chemistry and therefore needs the protection layer 847 to
be deposited to prevent chemical attack or modification as
mentioned previously. The layer 844 could be adversely affected by
high temperature exposure above 250.degree. C., 200.degree. C.,
150.degree. C., or in extreme cases 100.degree. C., such that
substrate 834 must be maintained at a low temperature to prevent
damage to layer 844. In this embodiment, layer 847 is deposited at
low temperature to prevent damage to features and layer 844. In
this case the source gases must be chosen such that the chemical
reaction can occur at a sufficient deposition rate to maintain an
economically feasible and short processing time. Compounds of
Formula I are examples of molecules which have sufficiently high
rates of reaction to provide for high deposition rates on the order
of 0.2 to 2.0 angstroms/cycle.
[0102] Processes disclosed herein are carried out under activating
conditions, such as using a plasma source, as described above. The
processing chamber may also rely on the use of thermal, chemical or
other suitable activation processes without the need for a plasma
reaction. Alternatively, iterative sequences of plasma and
non-plasma activation steps to deposit or etch thin layers of
materials may be used.
An Example of a Fabrication Process for Deposition of a Tin Oxide
Film
[0103] FIGS. 2A-2E illustrate schematically cross-sectional views
of a substrate 834 at different stages of an integrated circuit
fabrication sequence for making a tin oxide film. The substrate
834, as shown in FIG. 2A, may have a substantially planar surface.
Alternatively, the substrate may have patterned structures, a
surface having trenches, holes, or vias formed therein. The
substrate 834 may also have a substantially planar surface having a
structure formed thereon or therein at a desired elevation. While
the substrate 834 is illustrated as a single body, it is understood
that the substrate 834 may contain one or more material layers used
in forming semiconductor devices such as metal contacts, trench
isolations, gates, bit-lines, or any other interconnect features. A
substrate structure 850 denotes the substrate 834 together with
other material layers formed on the substrate 834.
[0104] The substrate 834 may comprise one or more metal layers, one
or more dielectric materials, semiconductor material, and
combinations thereof utilized to fabricate semiconductor devices.
For example, the substrate 834 may include an oxide material, a
nitride material, a polysilicon material, or the like, depending
upon application. In one embodiment where a memory application is
desired, the substrate 834 may include the silicon substrate
material, an oxide material, and a nitride material, with or
without polysilicon sandwiched in between.
[0105] In another embodiment, the substrate 834 may include a
plurality of alternating oxide and nitride materials (i.e.,
oxide-nitride-oxide (ONO)) deposited on a surface of the substrate
(not shown). In various embodiments, the substrate 834 may include
a plurality of alternating oxide and nitride materials, one or more
oxide or nitride materials, polysilicon or amorphous silicon
materials, oxides alternating with amorphous silicon, oxides
alternating with polysilicon, undoped silicon alternating with
doped silicon, undoped polysilicon alternating with doped
polysilicon, or updoped amorphous silicon alternating with doped
amorphous silicon. The substrate 834 may be any substrate or
material surface upon which film processing is performed. For
example, the substrate 834 may be a material such as crystalline
silicon, silicon oxide, silicon oxynitride, silicon nitride,
strained silicon, silicon germanium, tungsten, titanium nitride,
doped or undoped polysilicon, doped or undoped silicon wafers and
patterned or non-patterned wafers, silicon on insulator (SOI),
carbon doped silicon oxides, silicon nitrides, doped silicon,
germanium, gallium arsenide, glass, sapphire, low k dielectrics,
and combinations thereof.
[0106] FIG. 2A illustrates a cross-sectional view of a substrate
structure 850 having a material layer 844 that has been previously
formed thereon. The material layer 844 may be a dielectric
material, for example an oxide layer, such as a low-k carbon
containing dielectric layer, a porous silicon oxycarbide low-k or
ultra low-k dielectric layer.
[0107] FIG. 2B depicts a tin oxide layer 847 deposited on the
substrate structure 850 of FIG. 2A. The tin oxide layer 847 may be
useful as a pattern transfer layer, or a hard mask, for subsequent
etch processes. The tin oxide layer 847 is formed on the substrate
structure 850 by any suitable deposition process, such as via PEALD
(plasma-enhanced atomic layer deposition), as will be discussed in
more detail below. Depending on the etch chemistry of the energy
sensitive resist material 808 used in the fabrication sequence, an
optional capping layer (not shown) may be formed on the tin oxide
layer 847 prior to the formation of energy sensitive resist
material 808. The optional capping layer functions as a mask for
the tin oxide layer 847 when the pattern is transferred therein and
protects amorphous carbon layer 847 from energy sensitive resist
material 808.
[0108] As depicted in FIG. 2B, energy sensitive resist material 808
is formed on the tin oxide layer 847. The layer of energy sensitive
resist material 808 can be spin-coated on the substrate to a
desired thickness. Most energy sensitive resist materials are
sensitive to ultraviolet (UV) radiation having a wavelength less
than about 450 nm, and for some applications having wavelengths of
245 nm or 193 nm. The energy sensitive resist material 808 may be a
polymer material or a carbon-based polymer.
[0109] A pattern is introduced into the layer of energy sensitive
resist material 808 by exposing energy sensitive resist material
808 to UV radiation through a patterning device, such as a mask,
and subsequently developing energy sensitive resist material 808 in
an appropriate developer. After energy sensitive resist material
808 has been developed, a defined pattern of through openings 840
is present in energy sensitive resist material 808, as shown in
FIG. 2C.
[0110] Thereafter, referring to FIG. 2D, the pattern defined in
energy sensitive resist material 808 is transferred through the tin
oxide layer 847 using the energy sensitive resist material 808 as a
mask. An appropriate chemical etchant is used that selectively
etches the tin oxide layer 847 over the energy sensitive resist
material 808 and the material layer 844, extending openings 840 to
the surface of material layer 844. Appropriate chemical etchants
may include reducing or halogenated chemistries including but not
limited to hydrogen, ammonia, and various chlorine containing
molecules.
[0111] Referring to FIG. 2E, the pattern is then transferred
through material layer 844 using the tin oxide layer 847 as a
hardmask. In this process step, an etchant is used that selectively
removes material layer 844 over the tin oxide layer 847. After the
material layer 844 is patterned, the tin oxide layer 847 can
optionally be stripped from the substrate 834.
Examples of Deposition Processes
[0112] FIG. 3 is a process flow diagram depicting a method for
depositing a tin oxide film according to an embodiment. FIGS. 2A-2E
are schematics showing cross-sectional views of a substrate at
different stages of an integrated circuit fabrication sequence.
[0113] It should be noted that the sequence of steps illustrated
are not intended to be limiting as to the scope of Formula I
described herein, since one or more steps may be added, deleted
and/or reordered without deviating from the basic scope of the
invention.
[0114] The method 100 begins at block 110 by providing a substrate
having a material layer deposited thereon. The substrate and the
material layer may be the substrate 834 and the material layer 844
as shown in FIGS. 2A and 2B.
[0115] At block 120, a compound of Formula I is flowed into the
processing volume from a metal precursor source. The metal
containing precursor is allowed sufficient residence time to adhere
to the substrate surface 834, after which an oxidant is flowed into
the processing volume. Suitable oxidants include, but are not
limited to, compounds such as H.sub.2O in the gaseous phase,
H.sub.2O.sub.2 in the gaseous phase, O.sub.2, O.sub.3, NO,
NO.sub.2, CO, and CO.sub.2.
[0116] At block 130, a plasma is generated in the interior
processing volume, allowing the compound of Formula I to react with
the ionized oxidizing gases to form a tin oxide layer on the
material layer.
[0117] The tin oxide layer may be formed by any suitable deposition
process, such as a plasma-enhanced chemical vapor deposition
(PECVD) process or a plasma-enhanced atomic layer deposition
(PEALD) process. Alternatively, the plasma-enhanced thermal
decomposition or reactive process as discussed above may not be
used. Instead, the substrate is exposed to the gas mixture of the
carbon-containing precursor, the compound of embodiments of the
invention, and the reducing agent in the processing volume, which
is maintained at an elevated temperature suitable for thermal
decomposition of the gas mixture. Other deposition processes, such
as a metal-organic CVD (MOCVD) process and atomic layer deposition
(ALD) process may also be used to form the deposited
metal-oxide.
[0118] Certain or all of the processes described in blocks 120 to
130 of FIG. 3 may be repeated until a desired thickness is reached.
Thickness of the tin oxide layer 847 is variable, depending upon
the stage of processing. In one embodiment, the tin oxide layer 847
may have a thickness from about 50 .ANG. to about 500 .ANG., such
as about 100 .ANG. to about 200 .ANG. such that the tin oxide layer
can be consumed during the main etch process with excellent
hardmask performance (e.g., good CD control and feature profile).
The resulting tin oxide hardmask may be used in various
applications such as deep oxide contact etches, DRAM capacitor mold
etches, and line and/or space etches. In the case of the line and
space etch applications such as shallow trench isolation etch
hardmask, gate etch hardmask and bit-line etch hardmask, the tin
oxide layer may have about 100 .ANG. to about 200 .ANG.. Depending
upon the etch selectivity of the dense and isolated regions, the
thickness of the layers may be tuned accordingly.
[0119] Once a tin oxide layer 847 with a desired thickness is
deposited on the material layer 844, the substrate may be subjected
to additional processes, such as the deposition process to form an
energy sensitive resist material 808 on the tin oxide layer 847,
and/or patterning process, as discussed above. The tin oxide layer
847 may be patterned using a standard photoresist patterning
techniques. The metal tin oxide layer 847 may be removed using a
solution comprising hydrogen peroxide and sulfuric acid. One
solution comprising hydrogen peroxide and sulfuric acid is known as
Piranha solution or Piranha etch. The tin oxide layer 847 may also
be removed using etch chemistries containing hydrogen, deuterium,
oxygen, and halogens (e.g. fluorine or chlorine), for example,
Cl.sub.2/O.sub.2, CF.sub.4/O.sub.2, Cl.sub.2/O.sub.2/CF.sub.4. A
purge process using a suitable purge gas, such as argon, nitrogen,
helium, or combination thereof, may be performed between the
processes described above to prevent unwanted condensation of the
gas or byproducts on the chamber walls or other component
components. The purge process may be performed with no application
of RF power.
[0120] In general, the following examples of deposition process
parameters may be used to form the tin oxide layer on a 300 mm
substrate. The process parameters may range from a wafer
temperature of about 25.degree. C. to about 700.degree. C., for
example, between about 200.degree. C. to about 500.degree. C.,
depending on the application of the hardmask film. The chamber
pressure may range from a chamber pressure of about 1 Torr to about
20 Torr, for example, between about 2 Torr and about 10 Torr. The
flow rate of the tin oxide-containing precursor may be from about
100 sccm to about 5,000 sccm, for example, between about 400 sccm
and about 2,000 sccm. If a liquid source is used, the precursor
flow may be between about 50 mg/min to about 1000 mg/min. If a
gaseous source is used, the precursor flow may be between about 200
sccm to about 5000 sccm, for example about 200 sccm to about 600
sccm. The flow rate of a dilution gas may individually range from
about 0 sccm to about 20,000 sccm, for example from about 2,000
sccm to about 10,000 sccm. The flow rate of a plasma-initiating gas
may individually range from about 0 sccm to about 20,000 sccm, for
example from about 200 sccm to about 2,000 sccm. The flow rate of
the metal-containing precursor may be from about 1,000 sccm to
about 15,000 sccm, for example, between about 5,000 sccm and about
13,000 sccm. The flow rate of the reducing agent may be from about
200 sccm to about 15,000 sccm, for example, between about 1,000
sccm and about 3,000 sccm.
[0121] Plasma may be generated by applying RF power at a power
density to substrate surface area of from about 0.001 W/cm2 to
about 5 W/cm2, such as from about 0.01 W/cm2 to about 1 W/cm2, for
example about 0.04 W/cm2 to about 0.07 W/cm2. The power application
may be from about 1 W to about 2,000 W, such as from about 10 W to
about 100 W, for a 300 mm substrate. RF power can be either single
frequency or dual frequency. A dual frequency RF power application
is believed to provide independent control of flux and ion energy
since the energy of the ions hitting the film surface influences
the film density. The applied RF power and use of one or more
frequencies may be varied based upon the substrate size and the
equipment used. If a single frequency power is used, the frequency
power may be between about 10 KHz and about 30 MHz, for example
about 13.56 MHz or greater, such as 27 MHz or 60 MHz. If a
dual-frequency RF power is used to generate the plasma, a mixed RF
power may be used. The mixed RF power may provide a high frequency
power in a range from about 10 MHz to about 60 MHz, for example,
about 13.56 MHz, 27 MHz or 60 MHz, as well as a low frequency power
in a range of from about 10 KHz to about 1 MHz, for example, about
350 KHz. Electrode spacing, i.e., the distance between a substrate
and a showerhead, may be from about 200 mils to about 1000 mils,
for example, from about 280 mils to about 300 mils spacing.
[0122] The process range as discussed herein provides a typical
deposition rate for the tin oxide layer in the range of about 0.1
.ANG./cycle to about 2 .ANG./cycle and can be implemented on a 300
mm substrate in a deposition chamber from most commercially
available CVD and ALD processing chambers. The metal-doped oxide
layer may be deposited to a thickness between about 50 .ANG. and
about 500 .ANG., such as between about 100 .ANG. and about 200
.ANG..
[0123] Compounds of Formula I may also be used in spacer-defined
double patterning techniques, as illustrated in FIG. 4. The steps
for such a process are as follows: [0124] (a) Deposition of a layer
of (photo)resist onto a silicon substrate, then form a pattern in
the resist with Extreme Ultra Violet (EUV), Deep Ultra Violet
(DUV), or electron-beam (e-beam), or other lithography. The
photoresist is then developed to give the pattern. [0125] (b)
Deposit a spacer layer onto the resist using energy-enhanced ALD.
[0126] (c) Perform an anisotropic etch to remove the tops of the
features, using reactive ion etching (RIE) or ion milling (IM),
ideally leaving a square (non-rounded) corner to the spacer. [0127]
(d) Remove the photoresist, either by a wet or plasma etch. [0128]
(e) Anisotropically etch into the target layer (e.g. silicon).
[0129] (f) Remove the spacer, leaving your patterned substrate.
[0130] Compounds of Formula I may be prepared by processes known in
the art. The examples below are illustrative of such processes, but
are not intended to be limiting.
Example 1: Synthesis of Me.sub.3Sn(NMe.sub.2)
[0131] In a 250 mL flask was charged 20 mL of 2.5M Butyllithium
solution in hexane and 50 mL of anhydrous hexane. To the solution,
Me.sub.2NH gas was passed till fully reacted and the reaction
mixture was stirred for 2 hrs. The solution of 10 g of Me.sub.3SnCl
in 100 mL of anhydrous hexane was then added and the mixture was
stirred for 12 hrs. Filtration was carried out to remove solid. The
solvent was removed under reduced pressure. The liquid product was
purified by distillation under reduced pressure. NMR confirmed the
product to be Me.sub.3SnNMe.sub.2, as shown in FIG. 5.
Example 2: Synthesis of Sn(NMe.sub.2).sub.4
[0132] In a 250 mL flask was charged 80 mL of 2.5M Butyllithium
solution in hexane and 50 mL of anhydrous hexane. To the solution,
Me.sub.2NH gas was passed till fully reacted and the reaction
mixture was stirred for 2 hrs. The solution of 13 g of SnCl.sub.4
in 100 mL of anhydrous benzene was then added and the mixture was
refluxed for 4 hrs. Once cooled, filtration was carried out to
remove solid. The solvent was removed under reduced pressure. The
liquid product was purified by distillation under reduced pressure.
NMR confirmed the product to be Sn(NMe.sub.2).sub.4, as shown in
FIG. 6.
Example 3: Synthesis of Me.sub.2Sn(NEtMe).sub.2
[0133] Under inert atmosphere, a 1 L round bottom flask was charged
with 25.00 mL of 2.5M Butyllithium solution in hexane and 200 mL of
anhydrous hexane, followed by a slow addition of 5.40 mL of HNEtMe
in 100 mL of anhydrous hexane. The reaction mixture was then
stirred at room temperature for 1 h. The solution of 6.70 g of
Me.sub.2SnCl.sub.2 in 200 mL of anhydrous benzene was then added to
the flask (while cooled in the ice bath), and the reaction mixture
was left stirring at room temperature overnight. The solvent was
removed under reduced pressure from the filtrate. The liquid
product was isolated by distillation under reduced pressure
(80.degree. C. at 9.8.times.10.sup.-2 Torr). As shown in FIG. 7,
the product was confirmed to be Me.sub.2Sn(NEtMe).sub.2 by NMR
spectroscopy.
1)nBuLi+HNEtMe.fwdarw.LiNEtMe+butane Formula II
2) Me.sub.2SnCl.sub.2+2
LiNEtMe.fwdarw.Me.sub.2Sn(NEtMe).sub.2+2LiCl Formula III
Example 4: Synthesis of Bu.sub.2Sn(NMe.sub.2).sub.2
[0134] In a 250 mL flask was charged 24 mL of 2.5M Butyllithium
solution in hexane and 100 mL of anhydrous hexane. To the solution,
Me.sub.2NH gas was passed till fully reacted and the reaction
mixture was stirred for 2 hrs. The solution of 9.11 g of
Bu.sub.2SnCl.sub.2 in 100 mL of anhydrous benzene was then added
and the mixture was stirred for 4 hrs. Filtration was carried out
to remove solid. The solvent was removed under reduced pressure.
The liquid product was purified by distillation under reduced
pressure. NMR confirmed the product to be
Bu.sub.2Sn(NMe.sub.2).sub.2, as shown in FIG. 8.
Example 5: Synthesis of Me.sub.2SnEt.sub.2
[0135] 6.59 g of Me.sub.2SnCl.sub.2 was dissolved in 100 mL of
anhydrous ether, followed by the addition of 30 mL of 3M EtMgBr
under N.sub.2. After stirring for 4 hrs, mixture was treated with
0.1MHCl solution and organic layer was collected. The collected
organic layer was then treated with saturated NaHCO3 solution and
organic layer is collected. Distillation under N.sub.2 was carried
out to remove ether. Purification was carried out by distillation
under reduced pressure. As shown in FIG. 9, NMR confirmed the
product to be Me.sub.2SnEt.sub.2.
Example 6: Synthesis of Me.sub.4Sn
[0136] To the solution of 23.5 g of SnCl.sub.4 in ether was added
150 mL of 3M MeMgI under N.sub.2. After stirring for 4 hrs, mixture
was treated with 0.1 M HCl solution and organic layer was
collected. The collected organic layer was then treated with
saturated NaHCO.sub.3 solution and organic layer is collected.
Fractional distillation was carried out to remove ether.
Purification was carried out by distillation under reduced
pressure. As shown in FIG. 10, NMR confirmed the product to be
Me.sub.4Sn.
Example 7: Synthesis of Bu.sub.2Sn(OMe).sub.2
[0137] To a 250 mL flask was charged 20 g of Bu.sub.2SnCl.sub.2 and
20 mL of anhydrous methanol, followed by the addition of 7 g of
sodium methoxide in 30 mL of anhydrous methanol. The resulting
mixture was refluxed for 12 hrs. Filtration was carried out to
remove solid. The solvent was removed under reduced pressure. The
liquid product was purified by distillation under reduced pressure.
As shown in FIG. 11, NMR confirmed the product to be
Bu.sub.2Sn(OMe).sub.2.
Example 8: Synthesis of Bu.sub.2Sn(OAc).sub.2
[0138] Sodium acetate was first made by adding 6 g acetic acid into
a solution of 5.4 g of sodium methoxide in 30 mL of anhydrous
methanol. This was then added into the mixture of 30 g of
Bu.sub.2SnCl.sub.2 in 30 mL of anhydrous methanol. The resulting
mixture was refluxed for 4 hrs. Filtration was carried out to
remove solid. The solvent was removed under reduced pressure. The
liquid product was purified by distillation under reduced pressure.
As shown in FIG. 12, NMR confirmed the product to be
Bu.sub.2Sn(OAc).sub.2.
Example 9: Synthesis of Et.sub.2Sn(NMe.sub.2).sub.2
[0139] A 1 L flask was charged with 22 mL of 2.5M Butyllithium
solution in hexane and 400 mL of anhydrous hexane. Me.sub.2NH gas
was passed through the solution, and the reaction mixture was
stirred for 1 h. The solution of 6.71 g of Et.sub.2SnCl.sub.2 in
100 mL of anhydrous benzene was then added and the mixture was
stirred for 4 hrs. Filtration was carried out to remove any solid
products. The solvent was removed under reduced pressure from the
filtrate. The liquid product was purified by distillation under
reduced pressure. As shown in FIG. 13, NMR confirmed the product to
be Et.sub.2Sn(NMe.sub.2).sub.2.
Example 10: Synthesis of Me.sub.2Sn(NEt.sub.2).sub.2
[0140] In a 250 mL flask was charged 24 mL of 2.5M Butyllithium
solution in hexane and 50 mL of anhydrous hexane, followed by the
addition of 4.39 g of Et.sub.2NH. The reaction mixture was stirred
for 2 hrs. The solution of 6.59 g of Me.sub.2SnCl.sub.2 in 100 mL
of anhydrous ether was then added and the mixture was stirred for 4
hrs. Filtration was carried out to remove solid. The solvent was
removed under reduced pressure. The liquid product was purified by
distillation under reduced pressure. As shown in FIG. 14, NMR
confirmed the product to be Me.sub.2Sn(NEt.sub.2).sub.2.
Example 11: Synthesis of Sn(Pyrrolidinyl).sub.4
[0141] Under inert atmosphere, a 100 mL round bottom flask was
charged with 0.5 mL of Sn(NMe.sub.2).sub.4 and 25 mL of anhydrous
hexane, followed by a drop-wise addition of 1.1 mL of pyrrolidene.
After stirring the reaction mixture at room temperature for 2 h,
the solvent was removed via distillation under reduced pressure.
The residue remaining in the reaction flask was confirmed to be
Sn(Pyrrolodinyl).sub.4 by NMR spectroscopy, as shown in FIG.
15.
Example 12: Synthesis of Bu.sub.2Sn(Pyrrolodinyl).sub.2
[0142] Under inert atmosphere, a 1 L round bottom flask was charged
with 25 mL of 2.5M Butyllithium solution in hexane and 200 mL of
anhydrous hexane, followed by a slow addition of 5.3 mL of
pyrrolidene in 25 mL of anhydrous hexane. The reaction mixture was
then stirred at room temperature for 1 h, and then placed into the
ice bath. The solution of 9.46 g of Bu.sub.2SnCl.sub.2 in 50 mL of
anhydrous hexane was then added to the flask, and the reaction
mixture was left stirring at room temperature for 2 h. Filtration
was carried out to remove any solid products. The solvent was
removed under reduced pressure from the filtrate. As shown in FIG.
16, the product was confirmed to be Bu.sub.2Sn(Pyrrolodinyl).sub.2
by NMR spectroscopy.
Example 13: Synthesis of Et.sub.2Sn(Pyrrolodinyl).sub.2
[0143] Under inert atmosphere, a 1 L round bottom flask was charged
with 5.3 mL of pyrrolidene and 200 mL of anhydrous pentane. Once
the reaction flask was placed in the ice bath, 25 mL of 2.5M
Butyllithium solution in hexane were slowly added to the reaction
flask while stirring vigorously. The reaction mixture was then
stirred at room temperature for 1 h, and then placed back into the
ice bath. The solution of 7.7 g of Et.sub.2SnCl.sub.2 in 100 mL of
anhydrous pentane and 20 mL of anhydrous benzene was then added to
the flask, and the reaction mixture was left stirring at room
temperature overnight. Filtration was carried out to remove any
solid products. The solvent was removed under reduced pressure from
the filtrate. Final product was purified via vacuum distillation.
As shown in FIG. 17, the product is confirmed to be
Et.sub.2Sn(Pyrrolodinyl).sub.2 by NMR spectroscopy.
Example 14: Synthesis of Me.sub.2Sn(NMe.sub.2).sub.2
[0144] Under inert atmosphere, a 1 L flask was charged with 25 mL
of 2.5M Butyllithium solution in hexane and 400 mL of anhydrous
hexane. The reaction flask was placed in the ice bath and
Me.sub.2NH gas was passed through the solution until a white slushy
solution was obtained (ca. 15 min). Afterwards the reaction mixture
was stirred for 1 h at room temperature. The reaction flask was
placed in the ice bath again and the solution of 6.7 g of
Me.sub.2SnCl.sub.2 in 100 mL of anhydrous benzene was slowly added,
and the mixture was stirred overnight at room temperature.
Filtration was carried out to remove any solid products. The
solvent was removed under reduced pressure from the filtrate. The
liquid product was purified by distillation under reduced pressure.
As shown in FIG. 18, the product is confirmed to be
Me.sub.2Sn(NMe.sub.2).sub.2 by NMR spectroscopy.
Example 15: Synthesis of tBuSn(NMe.sub.2).sub.3
[0145]
Sn(NMe.sub.2).sub.4+tBuLi.fwdarw.tBuSn(NMe.sub.2).sub.3+LiNMe.sub.-
2 Formula IV
[0146] Under inert atmosphere, a 5 L round bottom flask was charged
with 100 mL of Sn(NMe.sub.2).sub.4 and ca. 3 L of anhydrous hexane.
The mixture was stirred using a mechanical stirrer, and placed in
the ethylene-glycol bath at -15.degree. C. In the glovebox, a 1 L
flask was loaded with 200 mL of 1.7M tert-butyllithium solution in
anhydrous hexane, and ca. 200 mL of anhydrous hexane. The tBuLi
solution was then slowly added to the reaction flask. The reaction
mixture was stirred at room temperature for 3 h. The stirring was
then stopped, and salts were left to precipitate out of the
reaction mixture overnight. The liquid was cannulated into another
5 L round bottom flask. The solvents were removed via distillation,
and 62 g of the final product were isolated by distillation under
reduced pressure (120.degree. C., 6.2.times.10.sup.-2 Torr). As
shown in FIG. 19, the product was confirmed to be
tBuSn(NMe.sub.2).sub.3 by NMR spectroscopy. 90%
tBuSn(NMe.sub.2).sub.3 and 10% tBu.sub.2Sn(NMe.sub.2).sub.2.
[0147] Similarly, complexes of the type RSn(NEtMe).sub.3 can be
synthesized following the above procedure by reacting
Sn(NEtMe).sub.4 with RLi, where R=Et, iPr, iBu, nPr
Sn(NEtMe).sub.4+RLi.fwdarw.RSn(NEtMe).sub.3+LiNEtMe Formula V
[0148] where R=Et, iPr, iBu, nPr
Example 16:
Sn(NEtMe).sub.4+EtLi.fwdarw.EtSn(NEtMe).sub.3+LiNEtMe
[0149] Under inert atmosphere, a 5 L round bottom flask was charged
with 100 g of Sn(NEtMe).sub.4 and ca. 2.5 L of anhydrous hexane.
The mixture was stirred using a mechanical stirrer, and placed in
the ethylene-glycol bath at -15.degree. C. In the glovebox, a 1 L
flask was loaded with 655 mL of 0.5 M ethyllithium solution in
anhydrous benzene, and ca. 200 mL of anhydrous benzene. The EtLi
solution was then slowly added to the reaction flask. The reaction
mixture was stirred at room temperature for 3 h. The stirring was
then stopped, and salts were left to precipitate out of the
reaction mixture overnight. The liquid was cannulated into another
5 L round bottom flask. The solvents were removed via distillation,
and the final product isolated via distillation under reduced
pressure.
Example 17:
Sn(NEtMe).sub.4+iPrLi.fwdarw.iPrSn(NEtMe).sub.3+LiNEtMe
[0150] Under inert atmosphere, a 5 L round bottom flask was charged
with 100 g of Sn(NEtMe).sub.4 and ca. 2.5 L of anhydrous hexane.
The mixture was stirred using a mechanical stirrer, and placed in
the ethylene-glycol bath at -15.degree. C. In the glovebox, a 1 L
flask was loaded with 468 mL of 0.7 M isopropyllithium solution in
anhydrous pentane, and ca. 200 mL of anhydrous hexane. The iPrLi
solution was then slowly added to the reaction flask. The reaction
mixture was stirred at room temperature for 3 h. The stirring was
then stopped, and salts were left to precipitate out of the
reaction mixture overnight. The liquid was cannulated into another
5 L round bottom flask. The solvents were removed via distillation,
and the final product isolated via distillation under reduced
pressure.
Example 18:
Sn(NEtMe).sub.4+iBuLi.fwdarw.iBuSn(NEtMe).sub.3+LiNEtMe
[0151] Under inert atmosphere, a 5 L round bottom flask was charged
with 100 g of Sn(NEtMe).sub.4 and ca. 3 L of anhydrous hexane. The
mixture was stirred using a mechanical stirrer, and placed in the
ethylene-glycol bath at -15.degree. C. In the glovebox, a 1 L flask
was loaded with 193 mL of 1.7 M isobutyllithium solution in
anhydrous heptane, and ca. 200 mL of anhydrous hexane. The iBuLi
solution was then slowly added to the reaction flask. The reaction
mixture was stirred at room temperature for 3 h. The stirring was
then stopped, and salts were left to precipitate out of the
reaction mixture overnight. The liquid was cannulated into another
5 L round bottom flask. The solvents were removed via distillation,
and the final product isolated via distillation under reduced
pressure.
Example 19:
Sn(NEtMe).sub.4+nPrLi.fwdarw.nPrSn(NEtMe).sub.3+LiNEtMe
[0152] Under inert atmosphere, a 5 L round bottom flask was charged
with 100 g of Sn(NEtMe).sub.4 and ca. 3 L of anhydrous hexane. The
mixture was stirred using a mechanical stirrer, and placed in the
ethylene-glycol bath at -15.degree. C. In the glovebox, a 1 L flask
was loaded with 193 mL of 1.7 M n-propyllithium solution in
anhydrous heptane, and ca. 200 mL of anhydrous hexane. The nPrLi
solution was then slowly added to the reaction flask. The reaction
mixture was stirred at room temperature for 3 h. The stirring was
then stopped, and salts were left to precipitate out of the
reaction mixture overnight. The liquid was cannulated into another
5 L round bottom flask. The solvents were removed via distillation,
and the final product isolated via distillation under reduced
pressure.
Example 20: Comparative Reactivity Tests
[0153] a) [0154] To Sn(NMe.sub.2).sub.4 was added water. Reaction
took place spontaneously. The clear Sn(NMe.sub.2).sub.4 turned
cloudy and a white solid formed. [0155] To Sn(NMe.sub.2).sub.4 was
added anhydrous ethanol. The mixture warmed up and NMR confirmed
the complete replacement of --NMe.sub.2 group by --OEt group. More
ethanol was added and NMR was carried out to further confirm the
completion of the reaction (FIG. 20).
[0156] b) [0157] To Me.sub.3SnNMe.sub.2 was added water. NMR
indicated that no reaction took place. The mixture was heated at
50.degree. C. for 1 hr. NMR showed that reaction took place (FIG.
21). [0158] To Me.sub.3SnNMe.sub.2 was added anhydrous methanol.
NMR indicated that no reaction took place. The mixture was heated
at 50.degree. C. for 1 hr. The clear solution turned cloudy. NMR
confirmed that reaction had taken place.
[0159] c) [0160] To Bu.sub.2Sn(OAc).sub.2 was added water. Reaction
took place spontaneously. The clear Bu.sub.2Sn(OAc).sub.2 turned
cloudy and a white solid formed. [0161] To Bu.sub.2Sn(OAc).sub.2
was added anhydrous methanol. NMR showed that no reaction took
place (FIG. 22).
[0162] d) [0163] To Bu.sub.2Sn(OMe).sub.2 was added water. Reaction
took place spontaneously. The clear Bu.sub.2Sn(OMe).sub.2 turned
cloudy and a white solid formed. [0164] To Bu.sub.2Sn(OMe).sub.2
was added acetic acid. NMR shows that some --OMe group has been
replaced by --OAc group (FIG. 23).
[0165] e) [0166] To Bu.sub.2Sn(NMe.sub.2).sub.2 was added water.
Reaction took place spontaneously. The clear
Bu.sub.2Sn(NMe.sub.2).sub.2 turned cloudy and a white solid formed.
[0167] To Bu.sub.2Sn(NMe.sub.2).sub.2 was added Methanol. NMR shows
that some --NMe.sub.2 group has been replaced by --OMe group (FIG.
24).
Example 21: Thermal Stability Tests
[0168] Thermal stability tests of compounds of Formula I were
carried out in sealed glass ampoules, which were heated at a set
temperature for 1 hr. NMR was performed to see if there had been
any thermal decomposition. A visual check was also used, looking
for solid formation after heat treatment. FIG. 25 shows NMR of
Me.sub.4Sn before and after heating at 200.degree. C. There was no
significant change after heating at 200.degree. C. for 1 hr based
on both NMR and visual check.
[0169] FIG. 26 shows NMR of Et.sub.2Sn(NMe.sub.2).sub.2 before and
after heating at 200.degree. C. There was no significant change
after heating at 200.degree. C. for 1 hr based on both NMR and
visual check.
[0170] FIG. 27 shows NMR of Me.sub.2Sn(NMe.sub.2).sub.2 before and
after heating at 150.degree. C. There was no significant change
after heating at 150.degree. C. for 24 hr based on both NMR and
visual check.
[0171] FIG. 28 shows the decomposition temperature of
representative compounds of Formula I.
[0172] Table 1 below summarizes deposition and reactivity data for
illustrative compounds of Formula I.
TABLE-US-00001 TABLE 1 Reactivity Deposition (relative rate
Assignment Materials H.sub.2O Methanol Acetic acid ranking)
(A/cycle) 1 Me.sub.4Sn No No No 0.1 0.1-0.2 2 Me.sub.3Sn(NMe.sub.2)
Yes at 50 C., No at 50 C., Most likely, 0.5 0.25 No at RT No at RT
but form salt predicted Me.sub.2Sn(NMe.sub.2).sub.2 Yes Yes Yes 4
1.0-1.2 Me.sub.2Sn(NEtMe).sub.2 Yes Yes Yes 4 1.0-1.2 predicted 3
Bu.sub.2Sn(OAc).sub.2 Yes No N/A 2 0.4 predicted 4
Bu.sub.2Sn(OMe).sub.2 Yes Yes, partially 2.5 0.5 predicted 5
Bu.sub.2Sn(Pyrro).sub.2 Yes Yes Most likely, 2.5 0.5 but form salt
predicted 6 Bu.sub.2Sn(NMe.sub.2).sub.2 Yes Yes Most likely, 2.5
0.6 but form salt predicted 7 Sn(NMe.sub.2).sub.4 Yes Yes Most
likely, 3 0.8 but form salt predicted 8 Et.sub.2Sn(NMe.sub.2).sub.2
Yes Yes Yes 3 0.8 predicted
[0173] These results demonstrate that compounds of Formula I are
thermally stable, showing that delivery of the compound to the
deposition chamber will take place without observable decomposition
occurring.
Example 22: SnO.sub.2 Deposition Using
Me.sub.2Sn(NMe.sub.2).sub.2
[0174] Deposition of SnO.sub.2 was carried out using
Me.sub.2Sn(NMe.sub.2).sub.2 and an oxidizing plasma between 40 and
180.degree. C. with deposition rate of 1.4 to 0.8 .ANG. (angstrom)
per cycle achieved at 40 and 180.degree. C. respectively. Lower
temperature deposition is used to reduce the damage of the
underlying photo-resist, amorphous silicon or amorphous carbon
layers.
[0175] It was also found that symmetric molecules, such as
Me.sub.4Sn, has low reactivity and absorption characteristics to
allow it to function as an efficient ALD precursor, resulting in
only 0.1 .ANG./cycle deprates. In particular embodiments, examples
of molecules with improved effectiveness and efficiency are the
asymmetric molecules with higher reactivity and absorption and
surface reaction properties that lead to higher deprate films that
rival the benchmark of 1 A per ALD cycle like is known for common
SiO.sub.2 ALD precursors. Particular examples of asymmetric
molecules include Me.sub.2Sn(NMe.sub.2).sub.2 and
Me.sub.2Sn(NEtMe).sub.2, where final deposition rates are 0.8 to
1.4 .ANG./cycle depending on process conditions. The resulting cost
reduction for moving to the more reactive molecules is on the order
of 5-10 times cost reduction.
[0176] It was also found that keeping a single molecule of
Me.sub.2Sn(NMe.sub.2).sub.2 stable is difficult at temperatures
above 10.degree. C. To improve stability and preventing
decomposition, other Sn based compounds, for example
MeSn(NMe.sub.2).sub.3 or Sn(NMe.sub.2).sub.4 may be added in a
mixture with Me.sub.2Sn(NMe.sub.2).sub.2.
Multistage Distillation
[0177] Various forms of multistage distillation are known in the
chemical manufacturing industry, but have not been employed for the
purification of organometallic materials that include tetramethy
tin or other compounds of Formula I.
[0178] As illustrated by the schematic shown in FIG. 29,
multiple-effect or multistage distillation (MED) is a distillation
process often used for sea water desalination. It consists of
multiple stages or "effects". (In schematic in FIG. 29 the first
stage is at the top. Pink areas are vapor, lighter blue areas are
liquid feed material. The turquoise represents condensate. It is
not shown how feed material enters other stages than the first,
however those should be readily understood. F--feed in. S--heating
steam in. C--heating steam out. W--purified material (condensate)
out. R--waste material out. O--coolant in. P--coolant out. VC is
the last-stage cooler.) In each stage the feed material is heated
by steam in tubes. Some of the feed material evaporates, and this
steam flows into the tubes of the next stage, heating and
evaporating more of the distillate. Each stage essentially reuses
the energy from the previous stage.
[0179] The plant can be seen as a sequence of closed spaces
separated by tube walls, with a heat source at one end and a heat
sink at the other. Each space consists of two communicating
subspaces, the exterior of the tubes of stage n and the interior of
the tubes in stage n+1. Each space has a lower temperature and
pressure than the previous space, and the tube walls have
intermediate temperatures between the temperatures of the fluids on
each side. The pressure in a space cannot be in equilibrium with
the temperatures of the walls of both subspaces; it has an
intermediate pressure. As a result, the pressure is too low or the
temperature too high in the first subspace, and the feed material
evaporates. In the second subspace, the pressure is too high or the
temperature too low, and the vapor condenses. This carries
evaporation energy from the warmer first subspace to the colder
second subspace. At the second subspace the energy flows by
conduction through the tube walls to the colder next space.
[0180] As shown by Table 2 below, purification of SnMe.sub.4 by
multistage distillation results in a compound having significantly
lower levels of impurities compared to that purified by
conventional means.
TABLE-US-00002 TABLE 2 Single Single Average stage stage single
Delta Multi vs Multistage option 1 option 2 stage Single Element
ppb ppb ppb ppb ppb % difference Ag 5 10 5 7.5 -33% Al 5 40 20 30
-83% As 50 50 100 75 -33% Au 10 10 5 7.5 33% B 40 70 10 40 0% Be 1
1 5 3 -67% Bi 1 2 5 3.5 -71% Ca 80 270 100 185 -57% Cd 1 1 5 3 -67%
Co 0 1 5 3 -100% Cr 2 3 5 4 -50% Cu 4 12 5 8.5 -53% Fe 11 31 10
20.5 -46% Hf 0 0 5 2.5 -100% K 30 30 20 25 20% Li 2 5 50 27.5 -93%
Mg 8 35 50 42.5 -81% Mn 0.5 0.5 5 2.75 -82% Mo 0.5 1.8 5 3.4 -85%
Na 200 200 100 150 33% Nb 0.5 0.5 5 2.75 -82% N 150 150 5 77.5 94%
Pb 0.4 2.1 2 2.05 -80% Pd 0.5 0.5 5 2.75 -82% Pt 2 2 5 3.5 -43% Rb
1 1 5 3 -67% Re 0.5 0.5 5 2.75 -82% Rh 0.5 0.5 5 2.75 -82% Ru 0.5
0.5 5 2.75 -82% Sb 20 120 250 185 -89%
[0181] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. The terms "comprising,"
"having," "including," and "containing" are to be construed as
open-ended terms (i.e., meaning "including, but not limited to,")
unless otherwise noted. The term "connected" is to be construed as
partly or wholly contained within, attached to, or joined together,
even if there is something intervening.
[0182] The recitation of ranges of values herein are merely
intended to serve as a shorthand method of referring individually
to each separate value falling within the range, unless otherwise
indicated herein, and each separate value is incorporated into the
specification as if it were individually recited herein.
[0183] All methods described herein can be performed in any
suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate embodiments of the invention
and does not impose a limitation on the scope of the invention
unless otherwise claimed. The various embodiments and elements can
be interchanged or combined in any suitable manner as
necessary.
[0184] No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of
the invention.
[0185] It will be apparent to those skilled in the art that various
modifications and variations can be made to the present invention
without departing from the spirit and scope of the invention. There
is no intention to limit the invention to the specific form or
forms disclosed, but on the contrary, the intention is to cover all
modifications, alternative constructions, and equivalents falling
within the spirit and scope of the invention, as defined in the
appended claims. Thus, it is intended that the present invention
cover the modifications and variations of this invention provided
they come within the scope of the appended claims and their
equivalents.
* * * * *