U.S. patent application number 10/660364 was filed with the patent office on 2004-08-05 for ion gun deposition and alignment for liquid-crystal applications.
Invention is credited to Callegari, Alessandro Cesare, Chaudhari, Praveen, Doyle, James Patrick, Galligan, Eileen Ann, Kato, Yoshimine, Lacey, James Andrew, Lien, Shui-Chih Alan, Lu, Minhua, Nakano, Hiroki, Odahara, Shuichi.
Application Number | 20040151911 10/660364 |
Document ID | / |
Family ID | 24438046 |
Filed Date | 2004-08-05 |
United States Patent
Application |
20040151911 |
Kind Code |
A1 |
Callegari, Alessandro Cesare ;
et al. |
August 5, 2004 |
Ion gun deposition and alignment for liquid-crystal
applications
Abstract
An apparatus for depositing and aligning an amorphous film in a
single step, a method of forming an aligned film on a substrate in
a single step by combining the deposition and alignment of an
alignment layer into a single-step using ion beam processing and an
amorphous film having an aligned atomic structure prepared by a
method in which an aligned film is deposited and aligned in a
single step are provided. The film is deposited and aligned in a
single step by bombarding a substrate with an ion beam at a
designated incident angle to simultaneously (a) deposit the film
onto the substrate and (b) arrange an atomic structure of the film
in at least one predetermined aligned direction.
Inventors: |
Callegari, Alessandro Cesare;
(Yorktown Heights, NY) ; Chaudhari, Praveen;
(Briarcliff Manor, NY) ; Doyle, James Patrick;
(Bronx, NY) ; Galligan, Eileen Ann; (Fishkill,
NY) ; Kato, Yoshimine; (Kanagawa, JP) ; Lacey,
James Andrew; (Mahopac, NY) ; Lien, Shui-Chih
Alan; (Briarcliff Manor, NY) ; Lu, Minhua;
(Mohegan Lake, NY) ; Nakano, Hiroki; (Shiga,
JP) ; Odahara, Shuichi; (Kanagawa-Ken, JP) |
Correspondence
Address: |
PAUL D. GREELEY, ESQ.
OHLANDT, GREELEY, RUGGIERO & PERLE, L.L.P.
10th FLOOR
ONE LANDMARK SQUARE
STAMFORD
CT
06901-2682
US
|
Family ID: |
24438046 |
Appl. No.: |
10/660364 |
Filed: |
September 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10660364 |
Sep 11, 2003 |
|
|
|
09608798 |
Jun 30, 2000 |
|
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6632483 |
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Current U.S.
Class: |
428/408 |
Current CPC
Class: |
C23C 14/3442 20130101;
C23C 14/225 20130101; G02F 1/133734 20130101; C23C 14/5833
20130101; Y10T 428/30 20150115; C23C 14/221 20130101; C23C 14/0605
20130101; G02F 1/13378 20130101 |
Class at
Publication: |
428/408 |
International
Class: |
B32B 009/00 |
Claims
What is claimed is:
1. An amorphous film having an aligned atomic structure disposed on
a substrate prepared by a method comprising the step of: bombarding
said substrate with at least one ion beam from at least one ion
beam source at a designated incident angle, wherein said ion beam
has an energy from about 100 to 300 eV and said designated incident
angle is from about 25 to about 60 degrees and wherein said
amorphous film is a diamond-like carbon film, to simultaneously (a)
deposit said amorphous film onto said substrate, and (b) arrange
said atomic structure of said amorphous film in at least one
predetermined aligned direction.
2. The amorphous film of claim 1, wherein said designated incident
angle produces a net deposition on a surface of said substrate.
3. The amorphous film of claim 1, wherein said ion beam comprises
impinging species and wherein the energy of said impinging species
is kept below the energy required for etching said amorphous film
on a surface of said substrate.
4. The amorphous film of claim 1, wherein said ion beam is
generated by a process comprising the steps of: introducing a
carbon-containing gas into a discharge chamber of a source of said
ion beam; ionizing said carbon-containing gas in said discharge
chamber to produce said ion beam comprising ions; and applying
sufficient voltage to said ion beam to accelerate said ions out of
said ion beam source.
5. The amorphous film of claim 4, wherein said ion beam has an
energy from about 200 to 300 eV.
6. The amorphous film of claim 1, wherein said ion beam is
generated using an ion gun.
7. The amorphous film of claim 1, wherein said ion beam further
comprises neutral molecules.
8. The amorphous film of claim 1, wherein said bombarding is
carried out simultaneously using a first ion beam and a second ion
beam.
9. The amorphous film of claim 8, wherein said designated incident
angle in said first ion beam is different from the designated
incident angle of said second ion beam.
10. The amorphous film of claim 1, wherein said designated incident
angle varies over time.
11. The amorphous film of claim 1, wherein said amorphous film is
optically transparent in the visible spectrum.
12. The amorphous film of claim 1, further comprising the step of:
placing a collimnator in the path of said ion beam between said
substrate and said ion beam source at a designated incident angle
to sputter material of said collimnator onto said substrate.
13. The amorphous film of claim 1, further comprising the step of:
moving said substrate or said ion beam source relative to the other
over time.
14. An amorphous film having an aligned atomic structure disposed
on a substrate prepared by a method comprising the step of:
bombarding a collimnator placed in the path of an ion beam from an
ion beam source between said substrate and said ion beam source at
a designated incident angle, wherein said ion beam has an energy
from about 100 to 300 eV and said designated incident angle is from
about 25 to about 60 degrees and wherein said amorphous film is a
diamond-like carbon film, to sputter material of said collimnator
onto said substrate and to simultaneously (a) deposit said
amorphous film onto said substrate and (b) arrange said atomic
structure of said amorphous film in at least one predetermined
aligned direction.
15. An amorphous film having an aligned atomic structure disposed
on a substrate prepared by a method comprising the steps of:
introducing a carbon-containing gas into a discharge chamber of an
ion beam source; ionizing said carbon-containing gas in said
discharge chamber to produce an ion beam comprising ions; applying
sufficient voltage to said ion beam to accelerate said ions out of
said ion beam source; and bombarding said substrate with at least
one ion beam from at least one ion beam source at a designated
incident angle, wherein said ion beam has an energy from about 100
to 300 eV and said designated incident angle is from about 25 to
about 60 degrees and wherein said amorphous film is a diamond-like
carbon film, to simultaneously (a) deposit said amorphous film onto
said substrate, and (b) arrange said atomic structure of said
amorphous film in at least one predetermined aligned direction.
16. An apparatus for depositing an amorphous film having an aligned
atomic structure on a substrate, comprising: at least one ion beam
source disposed at a designated incident angle of from about 25 to
about 60 degrees capable of producing at least one ion beam having
an energy from about 100 to 300 eV for bombarding said substrate
with said ion beam to simultaneously (a) deposit said amorphous
film onto said substrate, and (b) arrange said atomic structure of
said amorphous film in at least one predetermined aligned
direction.
17. The apparatus of claim 16, wherein said amorphous film is
optically transparent in the visible spectrum
18. The apparatus of claim 16, wherein said amorphous film is a
diamond-like carbon film.
19. The apparatus of claim 16, wherein said designated incident
angle produces a net deposition on a surface of said substrate.
20. The apparatus of claim 16, wherein said ion beam comprises
impinging species and wherein the energy of said impinging species
is kept below the energy required for etching said amorphous film
on a surface of said substrate.
21. The apparatus of claim 16, wherein said ion beam is generated
by a process comprising the steps of: introducing a
carbon-containing gas into a discharge chamber of a source of said
ion beam; ionizing said carbon-containing gas in said discharge
chamber to produce said ion beam comprising ions; and applying
sufficient voltage to said ion beam to accelerate said ions out of
said ion beam source.
22. The apparatus of claim 16, wherein said ion beam has an energy
from about 200 to 300 eV.
23. The apparatus of claim 16, wherein said ion beam source is an
ion gun.
24. The apparatus of claim 16, wherein said ion beam further
comprises neutral molecules.
25. The apparatus of claim 16, further comprising: means for moving
said substrate relative to said ion beam source.
26. The apparatus of claim 16, further comprising: means for moving
said ion beam source relative to said substrate.
27. The apparatus of claim 16, wherein said ion beam source
comprises a first ion beam source to produce a first ion beam and a
second ion beam source to produce a second ion beam for bombarding
simultaneously with said first and said second ion beams.
28. The apparatus of claim 27, further comprising: means for moving
at least one ion beam source relative to the others and relative to
said substrate.
29. The apparatus of claim 27, further comprising: means for
varying said designated incident angle in said first or said second
ion beam such that said designated incident angle in said first or
said second ion beam is different from the designated incident
angle of the other.
30. The apparatus of claim 27, further comprising: means for
varying said designated incident angle in said first or said second
ion beam over time.
31. The apparatus of claim 27, further comprising: means for moving
said substrate or said ion beam source relative to the other over
time.
32. The apparatus of claim 16, further comprising: a collimnator in
the path of said ion beam between said substrate and said ion beam
source at a designated incident angle for sputtering material of
said collimnator onto said substrate.
33. The apparatus of claim 32, further comprising: means for moving
said substrate or said ion beam source relative to the other and to
said collimnator over time.
34. An apparatus for depositing an amorphous film having an aligned
atomic structure on a substrate, comprising: at least one ion beam
source disposed at a designated incident angle of from about 25 to
about 60 degrees capable of producing at least one ion beam having
an energy from about 100 to 300 eV; and a collimnator placed in the
path of said ion beam produced from said ion beam source between
said substrate and said ion beam source at a designated incident
angle with said ion beam for bombarding said collimnator to sputter
material of said collimnator onto said substrate and thereby
simultaneously (a) deposit said amorphous film onto said substrate
and (b) arrange said atomic structure of said amorphous film in at
least one predetermined aligned direction.
35. The apparatus of claim 34, wherein said ion beam is produced by
a method comprising the steps of: introducing a carbon-containing
gas into a discharge chamber of an ion beam source; ionizing said
carbon-containing gas in said discharge chamber to produce an ion
beam comprising ions; applying sufficient voltage to said ion beam
to accelerate said ions out of said ion beam source to produce at
least one ion beam from said ion beam source.
36. The apparatus of claim 34, wherein said amorphous film is
optically transparent in the visible spectrum
37. The apparatus of claim 34, wherein said amorphous film is a
diamond-like carbon film.
38. The apparatus of claim 35, wherein said designated incident
angle produces a net deposition on a surface of said substrate.
Description
[0001] This application is a Continuation-In-Part of and claims
priority from U.S. application Ser. No. 09/608,798, filed on Jun.
30, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an amorphous film having an
aligned atomic structure and an apparatus for making such an
amorphous aligned film. More particularly, the present invention
relates to an amorphous film having an aligned atomic structure
prepared by a method in which an aligned film is deposited and
aligned in a single step and to an apparatus for depositing and
aligning such as an amorphous film in a single step.
[0004] 2. Description of the Prior Art
[0005] The alignment of liquid crystal molecules on a surface is
one of the critical steps in the manufacturing of a liquid crystal
display. The industry-wide method for producing such alignment is
through the mechanical rubbing of a polyimide surface. This method
requires a physical contact between a roller or brush and the
polyimide surface. The rubbing process realigns the surface of the
polyimide, which then acts as an alignment template for the
orientation of the liquid crystal molecules in the preferred
direction.
[0006] This approach has several disadvantages. For example,
because the rubbing method is a contact technique, debris can be
generated during the rubbing process resulting in a low process
yield. Moreover, additional cleaning steps are generally required
to remove the debris. Also, as the roller or brush rubs the surface
of the display, electrostatic charges can build up which may
discharge through the thin film transistors (TFT) resulting in a
lowering of the process yield. Additionally, the rubbing process
requires a relatively soft layer in order to modify the surface in
a desired orientation. Thus, choice of materials that are suitable
for use in the rubbing process is limited.
[0007] U.S. Pat. No. 5,770,826 to Callegari et al., the contents of
which are incorporated herein by reference, describes the use of
low energy ion beams to align surfaces for liquid crystal
applications. In these cases, the alignment was performed on an
alignment layer deposited by a distinct and separate process. While
a wide variety of surfaces were found to be suitable for alignment
by an ion beam technique, the reference does not teach the
deposition of the alignment layer and the alignment of the layer in
a single step.
[0008] One of the main driving forces in the liquid crystal
industry is the constant reduction in the cost of production. In
both the alignment of a polyimide layer via mechanical
rubbing/brushing or the alignment of layers using ion beams as
described in the previously incorporated U.S. Pat. No. 5,770,826,
the alignment layer must be applied prior to the alignment
procedure. Consequently, the deposition of an alignment layer and
subsequent alignment of the alignment layer in separate process
steps introduces additional costs into the manufacturing
process.
[0009] The applicants have found that deposition and alignment of
such a layer can be accomplished in a single step, which
significantly reduces the manufacturing cost.
SUMMARY OF THE INVENTION
[0010] The present invention includes an apparatus for depositing
an amorphous film having an aligned atomic structure on a
substrate, including:
[0011] at least one ion beam source disposed at a designated
incident angle of from about 25 to about 60 degrees capable of
producing at least one ion beam having an energy from about 100 to
300 eV for bombarding the substrate with the ion beam to
simultaneously (a) deposit the amorphous film onto the substrate,
and (b) arrange the atomic structure of the amorphous film in at
least one predetermined aligned direction.
[0012] The present invention further includes an apparatus for
depositing an amorphous film having an aligned atomic structure on
a substrate, including:
[0013] at least one ion beam source disposed at a designated
incident angle of from about 25 to about 60 degrees capable of
producing at least one ion beam having an energy from about 100 to
300 eV; and
[0014] a collimnator placed in the path of the ion beam produced
from the ion beam source between the substrate and the ion beam
source at a designated incident angle with the ion beam for
bombarding the collimnator to sputter material of the collimnator
onto the substrate and thereby simultaneously (a) deposit the
amorphous film onto the substrate and (b) arrange the atomic
structure of the amorphous film in at least one predetermined
aligned direction.
[0015] The present invention further includes an amorphous film
having an aligned atomic structure disposed on a substrate prepared
by one of the following methods:
[0016] (a) a method including the step of:
[0017] bombarding the substrate with at least one ion beam from at
least one ion beam source at a designated incident angle, wherein
the ion beam has an energy from about 100 to 300 eV and the
designated incident angle is from about 25 to about 60 degrees and
wherein the amorphous film is a diamond-like carbon film, to
simultaneously (a) deposit the amorphous film onto the substrate,
and (b) arrange the atomic structure of the amorphous film in at
least one predetermined aligned direction; or
[0018] (b) a method including the step of:
[0019] bombarding a collimnator placed in the path of an ion beam
from an ion beam source between the substrate and the ion beam
source at a designated incident angle, wherein the ion beam has an
energy from about 100 to 300 eV and the designated incident angle
is from about 25 to about 60 degrees and wherein the amorphous film
is a diamond-like carbon film, to sputter material of the
collimnator onto the substrate and to simultaneously (a) deposit
the amorphous film onto the substrate and (b) arrange the atomic
structure of the amorphous film in at least one predetermined
aligned direction.
[0020] The method by which these films are prepared is a dry
deposition and alignment technique, which reduces the need for pre-
and post-wet processing. The present method is also a non-contact
deposition and alignment technique, which reduces any potential
contamination of the surface by extraneous debris, such as those
commonly encountered in the contact rubbing techniques of the prior
art.
[0021] Accordingly, the present invention provides a simple and
cost effective method of forming easily processed aligned films on
which liquid crystals can be aligned for use in wide viewing angle
liquid-crystal displays.
[0022] Applicants have found that when fabricated into display
cells, the alignment layers according to the present invention have
sufficient anchoring energies. In addition, the measured pre-tilt
angles of the films are typically about 4 degrees or less, which is
well within the range required for fabricated into display
cells.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic of an ion beam source.
[0024] FIG. 2 depicts the geometry of the ion source relative to
the substrate, wherein .theta. (theta) is the angle of
incidence.
[0025] FIG. 3 is a schematic of an embodiment with a fixed
substrate.
[0026] FIG. 4 is a schematic of an embodiment with a moving
substrate.
[0027] FIG. 5 is a schematic of an embodiment in which an aligned
film on a moving substrate is obtained using two ion sources.
[0028] FIG. 6 is a schematic of an embodiment employing two ion
guns in which an aligned film on a moving substrate is obtained by
a combination of sputter deposition and direct alignment.
[0029] FIG. 7 illustrates an embodiment with a single ion source in
which an aligned film on a moving substrate is obtained using a
collimnator.
DETAILED DESCRIPTION OF THE INVENTION
[0030] The present invention provides an apparatus for depositing
and aligning an amorphous film in a single step.
[0031] The present invention further provides a method of forming
an aligned film on a substrate in a single step by combining the
deposition and alignment of an alignment layer into a single-step
using ion beam processing.
[0032] The present invention still further provides an amorphous
film having an aligned atomic structure prepared by a method in
which an aligned film is deposited and aligned in a single
step.
[0033] The term "aligned film" refers to a film in which the atomic
or molecular structure of the film, or the atomic or molecular
surface structure thereof, has a predetermined direction or
orientation. According to the present invention, an alignment film
is deposited and the atomic or molecular structure of the alignment
film is aligned in at least one desired direction through use of an
ion beam.
[0034] Apparatus
[0035] The apparatus for depositing an amorphous film having an
aligned atomic structure includes:
[0036] at least one ion beam source disposed at a designated
incident angle of from about 25 to about 60 degrees capable of
producing at least one ion beam having an energy from about 100 to
300 eV for bombarding the substrate with the ion beam to
simultaneously (a) deposit the amorphous film onto the substrate,
and (b) arrange the atomic structure of the amorphous film in at
least one predetermined aligned direction.
[0037] The apparatus of the present invention employs an ion beam
source, for example, a broad beam ion source, for the deposition of
amorphous diamond-like carbon films and, at the same time, films
that are deposited by such a source are given an alignment
direction suitable for, for example, the fabrication of liquid
crystal displays.
[0038] The apparatus for fabricating such a film includes a vacuum
chamber within which an ion source would be located. The ion source
could be, for example, a broad beam Kaufman-type ion source within
which a hydrocarbon gas would be introduced such as methane or
acetylene.
[0039] Within the ion source, a plasma is generated which is
included of carbon ions as well as carbon containing complex ions,
for example CH.sub.x.sup.+ where x can assume a variety of values
depending upon the precursor gas as well as the operating
parameters of the ion source including gas pressure and operating
power of the ion source. The extraction of ions from the ion source
can be accomplished through the application of an electrical
potential between the ion source and the substrate that is to be
exposed to the ion beam.
[0040] Preferably, the extraction of ions for the purpose of
depositing a film and aligning the film in a pre-determine
orientation is typically in the range of 100 to 300 eV.
[0041] The energy of the impinging species on the surface of the
substrate must in all cases be kept below the sputter threshold as
above this level, a net removal of material will occur at the
substrate resulting in an etching of the surface. It should be
noted that some of the ions can be neutralized after they are
extracted from the ion source by, for example, charge exchange
neutralization, such that the energetic species that arrive at the
substrate will be a combination of ions and neutrals.
[0042] In order to impart a preferred orientation to the film that
is deposited and aligned on the surface of the substrate, the
geometry of the system is set such that the angle of incidence
between the ion source and the substrate is typically in the range
between 25 and 60 degrees.
[0043] The substrate that is to be processed by the described
apparatus can be either stationery with respect to the ion source
or it can be moved with respect to the ion source. If the
dimensions of the ion source are smaller than that of the substrate
to be exposed to the ion source, it is preferable that either the
ion source or sources or the substrate or substrates be moveable in
the range of a substrate where they impinge on the substrate as
both ions and neutral species. With the energy of the impinging
ions and neutrals chosen in the range of 100 to 300 eV, a net
deposition of a carbon containing films will be found on the
surface of the substrate.
[0044] The apparatus that is to be used for the deposition and
alignment of the amorphous film therefore incorporates one or more
ion beam sources that can be configured in a number of different
embodiments.
[0045] In the first, one or more ion sources can be held in a fixed
position with the substrate to be exposed to the ion beam source is
also held in a stationary position.
[0046] In a second embodiment, one or more ion sources can be held
in a fixed position while the substrates to be coated with the
aligned amorphous film are moved beneath the ion sources. In this
embodiment, substrates larger than the ion sources can be
processed.
[0047] In a third embodiment, the substrate or substrates to the
processed are held stationary whereas the ion sources are moved
relative to the substrates. Once again in this embodiment, the
movement of the ion sources allows for the processing of substrates
that are larger than the ion sources.
[0048] In a fourth embodiment of the apparatus either the
substrates or the ion sources are capable of movement, but the
angle of incidence of the ion sources relative to one another can
be the same or different. Thus, the angle of incidence of the ion
sources relative to one another can be fixed for the duration of
the process or it can be variable, i.e., changed during the
processing of the substrates.
[0049] In a fifth embodiment of the apparatus a collimnator is
incorporated in the apparatus. The collimnator is placed between
the ion sources and the substrate such that the position of the
collimnator allows for the sputtering of the collimnator. In this
embodiment, the sputtered material can be collected on the surface
of the substrate resulting in the growth of a film on the surface
and the growing film can be simultaneously aligned by the energetic
bombardment from the ion sources. In this embodiment, the ion beam
extracted from the ion source is not limited to hydrocarbon gases
and can include such species as argon and /or nitrogen. The
designated incident angle is chosen such that it produces a net
deposition on a surface of the substrate.
[0050] In all embodiments described herein above, the ion beam
source is preferably an ion gun and can further include neutral
molecules. The ion beam source can include a first ion beam source
to produce a first ion beam and a second ion beam source to produce
a second ion beam for bombarding simultaneously with the first and
the second ion beams.
[0051] The apparatus according to the present invention can include
means for moving the substrate relative to the ion beam source
and/or means for moving the ion beam source relative to the
substrate.
[0052] The apparatus can further include means for moving at least
one ion beam source relative to the others and relative to the
substrate.
[0053] The apparatus can still further include means for varying
the designated incident angle in the first or the second ion beam
such that the designated incident angle in the first or the second
ion beam is different from the designated incident angle of the
other. The designated incident angle is chosen such that it
produces a net deposition on a surface of the substrate.
[0054] The apparatus can additionally include means for varying the
designated incident angle in the first or the second ion beam over
time and/or means for moving the substrate or the ion beam source
relative to the other over time.
[0055] In a preferred embodiment, where the apparatus includes a
collimnator in the path of the ion beam between the substrate and
the ion beam source at a designated incident angle for sputtering
material of the collimnator onto the substrate, the apparatus
preferably includes:
[0056] at least one ion beam source disposed at a designated
incident angle of from about 25 to about 60 degrees capable of
producing at least one ion beam having an energy from about 100 to
300 eV; and
[0057] a collimnator placed in the path of the ion beam produced
from the ion beam source between the substrate and the ion beam
source at a designated incident angle with the ion beam for
bombarding the collimnator to sputter material of the collimnator
onto the substrate and thereby simultaneously (a) deposit the
amorphous film onto the substrate and (b) arrange the atomic
structure of the amorphous film in at least one predetermined
aligned direction.
[0058] In this embodiment the apparatus can further include means
for moving the substrate or the ion beam source relative to the
other and to the collimnator over time.
[0059] Method
[0060] Referring to FIG. 1, an ion beam source is shown. Through
gas inlet 1 a carbon-containing gas, preferably a hydrocarbon gas,
such as methane, is introduced into the plasma chamber 2, i.e.,
discharge chamber of an ion beam source.
[0061] The carbon-containing gas optionally can be mixed with an
inert gas, such as, argon or nitrogen such that argon and/or
nitrogen can be introduced along with the hydrocarbon gas into the
discharge chamber. The gas is ionized in the discharge chamber to
produce an ion beam 4 including atoms and ions, which are then
accelerated out of the ion source through the application of
accelerating voltages. Sufficient voltage is applied to the ion
beam 4 to accelerate the atoms and ions out of the ion beam
source.
[0062] An electron source 3 for beam neutralization is disposed,
for example, in close proximity along the path of the ion beam 4 to
neutralize the ion beam. Neutralization can also be accomplished
with a tungsten or tantalum wire strung across the ion beam source.
Upon electron neutralization of the beam using electron source 3,
the ion beam can further include neutral molecules in addition to
ions and atoms.
[0063] The energy of the impinging species is kept below a level
such that a net accumulation, i.e., net deposition, is recorded on
the substrate surface. The energy of the depositing species must be
below the energy required to permit deposition of an alignment
layer on the substrate. If this condition is not satisfied, then
the result will be a net etch, or at the very least, no net
deposition.
[0064] In these experiments, carbon energies below 500 eV were
used. Preferably, the ion beam has an energy from about 100 to 500
eV. However, higher energies are also possible as long as they
satisfy the constraints discussed above.
[0065] The deposition rate is a function of the sticking
coefficient of the deposited species as well as the number of
incident atoms at the substrate surface as a function of time. The
deposition rate of the film can be controlled by varying the ion
current density, the time of exposure of the surface to the ion
beam, or both.
[0066] The angle of incidence of the depositing energetic species,
i.e., the designated incident angle for bombardment, also controls
the alignment properties of the deposited film.
[0067] Referring to FIG. 2, the geometry of the ion source relative
to the substrate 11 is depicted, wherein .theta. (theta) is the
angle of incidence, which is the designated incident angle for
bombardment by ion beam 4. Preferably, the angle of incidence is
from about 10 to about 70 degrees. More preferably, the angle of
incidence is from about 25 to about 60 degrees.
[0068] Deposition and alignment can be accomplished in either a
static or dynamic mode of operation. As shown in FIG. 3, substrate
11 can be held fixed relative to the ion source 10 generating the
ion beam 4 during the process. Alternatively, as shown in FIG. 4,
substrate 11 can be moved relative to the ion source 10 in a
direction shown by arrows along the x-axis such that substrate 11
is bombarded by the ion beam during the process. Both of these
embodiments result in the deposition of an alignment layer for
liquid crystal display applications.
[0069] FIG. 5 shows an embodiment in which an aligned film on a
moving substrate is obtained using more than one source, i.e., two
ion sources.
[0070] In this embodiment, two ion guns are used to produce an
alignment layer. The first ion source, i.e., a deposition ion gun
20, preferably has a perpendicular or close to perpendicular
orientation with respect to the substrate 11. The second ion
source, i.e., an alignment ion gun 21, is oriented such that the
ion beam forms an angle .theta. (theta) with the substrate, as
shown in FIG. 5.
[0071] Preferably, the designated incident angle in the first ion
beam is different from designated incident angle of the second ion
beam. Typically, the angle between the substrate and the second ion
source is from about 25 to about 60 degrees. An angle of about 35
degrees is advantageously used to align the films.
[0072] In general, substrate 11 is moved relative to the ion
sources 20 and 21 in a direction shown by arrows along the x-axis
such that substrate 11 is bombarded by the ion beam during the
process. However, depending on the movement of the substrate or the
ion beam source, the designated incident angle used to both deposit
and to align can vary over time.
[0073] Other typical but non-limiting parameters are listed
below:
1 DEPOSITION GUN: Gas Flow: CH.sub.4: 6 sccm Ar: 3 sccm Operating
Pressure: 5 .times. 10.sup.-2 Pa Beam Energy: 300 eV Beam Current:
50 mA ALIGNMENT GUN: Gas Flows: Ar: 14 sccm Operating Pressure: 5
.times. 10.sup.-2 Pa Beam Energy: 200 eV Beam Current: 100 mA
[0074] FIG. 6 shows an embodiment employing two ion guns in which
an aligned film on a moving substrate is obtained by a combination
of sputter deposition and direct alignment.
[0075] Sputter ion gun 30 is directed at a sputter material target
32, which is then bombarded with atoms and ions from the sputter
ion gun resulting in a transfer of material from the target to the
substrate.
[0076] The target can be, but is not limited to, carbon. It is
highly desirable that the film is optically transparent in the
visible spectrum. Accordingly, a diamond-like carbon film is
preferred.
[0077] Preferably, the angle between the target and the substrate
is from 30 to 60 degrees. The operating parameters of the alignment
gun are similar to those described above. The alignment gun 31
provides desired alignment and imparts desired texture to the film.
Substrate 11 can be moved relative to the sputter material target
32 and ion source 31 in a direction shown by arrows along the
x-axis such that substrate 11 is bombarded by the sputter beam and
the ion beam during the process.
[0078] FIG. 7 illustrates an embodiment with a single ion source 40
in which an aligned film on substrate 11 is obtained using
collimnator 41, i.e., a "bee's nest collimnator, preferably
constructed of carbon. As above, substrate 11 moves relative to the
ion beam source over time in a direction shown by arrows along the
x-axis during the deposition and alignment.
[0079] In this embodiment, collimnator 41 is placed in the path of
the incident ion beam, which includes ions and atoms. A portion of
the incident energetic species will sputter the collimnator in a
forward direction, which will result in a net deposition of a film
on a surface of substrate 11 and, simultaneously, the ion beam
including ions and atoms that passes through the collimnator will
align the deposited layer in the same step.
[0080] Film
[0081] The present invention provides a simple and cost effective
method of forming easily processed aligned films. The amorphous
film of the present invention is optically transparent in the
visible spectrum.
[0082] Preferably, the amorphous film is prepared by the method of
the present invention. The method includes the step of: bombarding
the substrate with at least one ion beam from at least one ion beam
source at a designated incident angle to simultaneously (a) deposit
the amorphous film onto the substrate and (b) arrange the atomic
structure of the amorphous film in at least one predetermined
aligned direction.
[0083] Preferably, the ion beam has an energy from about 100 to 300
eV, more preferably, from about 200 to 300 eV, and the designated
incident angle is from about 25 to about 60 degrees. Preferably,
the amorphous film is a diamond-like carbon film.
[0084] The ion beam includes impinging species the energy of which
is kept below the energy required for etching the amorphous film on
a surface of the substrate. The designated incident angle is
selected such that it produces a net deposition on a surface of the
substrate.
[0085] The ion beam is generated using an ion gun and can further
include neutral molecules.
[0086] The bombarding can be carried out simultaneously using, for
example, a first ion beam and a second ion beam, such that the
designated incident angle in the first ion beam can be the same or
different from the designated incident angle of the second ion
beam. Further, the designated incident angles can be adapted to
vary over time. Thus, the method can further include moving the
substrate or the ion beam source relative to the other over
time.
[0087] The method can further include the placing a collimnator in
the path of the ion beam between the substrate and the ion beam
source at a designated incident angle to sputter material of the
collimnator onto the substrate. Thus, the film can be prepared by
bombarding a colimnator placed in the path of an ion beam from an
ion beam source between the substrate and the ion beam source at a
designated incident angle to sputter material of the collimnator
onto the substrate and to simultaneously (a) deposit the amorphous
film onto the substrate and (b) arrange the atomic structure of the
amorphous film in at least one predetermined aligned direction.
[0088] A liquid cell fabricated using a film deposited and aligned
with an ion source by the method of the present invention as the
alignment layer displayed excellent contrast. The following
parameters were used for the deposition and alignment:
2 Gas Flows: CH4: 10 sccm Ar: 1.5 sccm Operating Pressure: 5
.times. 10.sup.-2 Pa Beam Energy: 200 eV Beam Current: 100 mA
[0089] Surprisingly, the measured pre-tilt angle in this case was 4
degrees, which is well within the range required for fabricated
into display cells.
[0090] In addition, applicants have unexpectedly found that when
fabricated into display cells, the alignment layers prepared
according to the present invention have sufficient anchoring
energies.
[0091] Anchoring energy is defined as the energy, which describes
how good the liquid crystal directors are aligned to the alignment
direction of the alignment layer. The alignment direction in the
present case is the projection of the ion beam traveling direction
on the alignment layer surface. The higher the anchoring energy,
the closer the liquid crystal directors are aligned to the
alignment direction.
[0092] For most liquid crystal displays, a high anchoring energy is
necessary to obtain good optical performance. The rubbed polyimide
films used in current liquid crystal displays usually give an
anchoring energy of 1.0.times.10.sup.-3 N/m or higher, which is
considered to be strong anchoring. In contrast, non-contact
alignment methods usually give an anchoring energy less than that
of rubbed polyimide. The alignment layers prepared according to the
present invention unexpectedly produce an anchoring energy of
1.0.times.10.sup.-3 N/m or higher. This demonstrates that alignment
layers provided by the method of present invention are at least as
good as rubbed polyimide.
[0093] Thus, the present invention provides a simple and cost
effective method of forming easily processed aligned films on which
liquid crystals can be aligned to form flat panels suitable for use
as wide viewing angle liquid-crystal displays.
[0094] Although discussed in the context using the output of ion
beam source, in some embodiments a direct writing technique can be
used to direct the ion beam to desired regions to form a film
having an aligned atomic structure.
[0095] The present invention has been described with particular
reference to the preferred embodiments. It should be understood
that variations and modifications thereof can be devised by those
skilled in the art without departing from the spirit and scope of
the present invention. Accordingly, the present invention embraces
all such alternatives, modifications and variations that fall
within the scope of the appended claims.
* * * * *