U.S. patent application number 11/861519 was filed with the patent office on 2009-03-26 for process for forming thin film encapsulation layers.
Invention is credited to John A. Agostinelli, Michael L. Boroson, Elena A. Fedorovskaya, David H. Levy.
Application Number | 20090081356 11/861519 |
Document ID | / |
Family ID | 40351857 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090081356 |
Kind Code |
A1 |
Fedorovskaya; Elena A. ; et
al. |
March 26, 2009 |
PROCESS FOR FORMING THIN FILM ENCAPSULATION LAYERS
Abstract
A process is disclosed for making a thin film encapsulation
package for an OLED device by depositing a thin film material on an
OLED device to be encapsulated, comprising simultaneously directing
a series of gas flows along substantially parallel elongated output
openings, wherein the series of gas flows comprises, in order, at
least a first reactive gaseous material, an inert purge gas, and a
second reactive gaseous material, optionally repeated a plurality
of times, wherein the first reactive gaseous material is capable of
reacting with a substrate surface treated with the second reactive
gaseous material to form an encapsulating thin film, wherein the
first reactive gaseous material is a volatile organo-metal
precursor compound. The process is carried out substantially at or
above atmospheric pressure, and the temperature of the substrate
during deposition is under 250.degree. C.
Inventors: |
Fedorovskaya; Elena A.;
(Pittsford, NY) ; Boroson; Michael L.; (Rochester,
NY) ; Levy; David H.; (Rochester, NY) ;
Agostinelli; John A.; (Rochester, NY) |
Correspondence
Address: |
Andrew J. Anderson;Patent Legal Staff
Eastman Kodak Company, 343 State Street
Rochester
NY
14650-2201
US
|
Family ID: |
40351857 |
Appl. No.: |
11/861519 |
Filed: |
September 26, 2007 |
Current U.S.
Class: |
427/66 |
Current CPC
Class: |
C23C 16/403 20130101;
C23C 16/405 20130101; C23C 16/45574 20130101; H01L 51/5253
20130101; B05D 5/00 20130101; C23C 16/45551 20130101 |
Class at
Publication: |
427/66 |
International
Class: |
B05D 5/12 20060101
B05D005/12 |
Claims
1. A process of making a thin film encapsulation package for an
OLED device by atomic layer deposition of a thin film material on
an OLED device to be encapsulated, comprising simultaneously
directing a series of gas flows along substantially parallel
elongated output openings, wherein the series of gas flows
comprises, in order, at least a first reactive gaseous material, an
inert purge gas, and a second reactive gaseous material, optionally
repeated a plurality of times, wherein the first reactive gaseous
material is capable of reacting with a substrate treated with the
second reactive gaseous material to form an encapsulating thin
film, wherein the first reactive gaseous material is a volatile
organo-metal precursor compound, wherein the process is carried out
substantially at or above atmospheric pressure, and wherein the
temperature of the substrate during deposition is under 250.degree.
C.
2. The process of claim 1 wherein the OLED device comprises: (a) a
first electrode; (b) a second electrode; and (c) one or more
organic layers formed between the first electrode and the second
electrode, at least one organic layer being a light-emitting
layer.
3. The process of claim 1 wherein the thin film encapsulation
package comprises a single layer of a single inorganic
compound.
4. The process of claim 1 wherein the thin film encapsulation
package comprises either (a) at least one first layer of a first
inorganic compound and at least one second layer of a second
inorganic compound, or (b) a layer that is a mixture of a first
inorganic compound and a second inorganic compound.
5. The process of claim 4 wherein the first inorganic compound and
the second inorganic compound are independently selected from an
oxide, nitride, sulfide, and phosphide.
6. The process of claim 4 wherein at least one of the first and the
second inorganic compound is aluminum oxide.
7. The process of claim 4 wherein at least one of the first and the
second inorganic compound is an oxide or a nitride.
8. The process of claim 4 wherein the first and the second
inorganic compound comprises an element that is independently
selected from elements in Group 3A, 3B, 4A, and 4B of the Periodic
Table.
9. The process of claim 4 wherein the first and the second
inorganic compound comprises an element that is independently
selected from the group consisting of zinc, aluminum, titanium,
hafnium, silicon, zirconium, yttrium, and indium.
10. The process of claim 1 wherein there is a plurality of first
encapsulating thin films and/or plurality of second encapsulating
thin films in which the first and the second encapsulating thin
films alternate in a stack.
11. A method of forming an OLED device, comprising: (a) providing a
substrate with a first electrode and one or more organic layers
formed thereon, at least one organic layer being a light-emitting
layer; (b) forming a second electrode comprising a transparent
conductive oxide over the one or more organic layers opposite the
first electrode; and (c) forming a thin film encapsulation package
as in claim 1.
12. The method of claim 11, wherein the thin film encapsulation
package is formed at a temperature less than 140 degrees C.
13. The method of claim 11 wherein the OLED device is a
top-emitting OLED device, wherein the first electrode is a bottom
electrode and the second electrode is a top electrode.
14. The method of claim 11 wherein the thin film encapsulation
package further comprises a layer of parylene polymer.
15. The process of claim 1 wherein the series of gas flows are
provided by a deposition device comprising, a series of elongated
output openings, substantially in parallel, positioned over the
substrate in close proximity thereto, in an output face of the
deposition device, spaced within 1 mm from a surface of the
substrate subjected to deposition.
16. The process of claim 15 wherein there are no exhaust channels
between the series of elongated output openings for the first
reactive gaseous material and the second reactive gaseous
material.
17. The process of claim 15 wherein the deposition device further
comprises exhaust channels between substantially parallel elongated
output openings for the first and the second reactive gaseous
materials.
18. The process of claim 15 wherein the flows of one or more of the
gaseous materials to the substrate surface for thin film deposition
provides at least part of a force separating the output face of the
deposition device from the surface of the substrate.
19. The process of claim 1 wherein atomic layer deposition is
carried out in a deposition system sequentially comprising: (A) an
entrance section; (B) a coating section comprising: (i) a plurality
of sources for, respectively, a plurality of gaseous materials
comprising at least the first reactive gaseous material, the second
reactive gaseous material, and the inert purge gas, respectively;
(ii) at least one delivery head for delivering the plurality of
gaseous materials to the substrate receiving thin film deposition,
the delivery head comprising: (a) a plurality of inlet ports
comprising at least a first, a second, and a third inlet port for
receiving the first reactive gas material, the second reactive
gaseous material, and the inert purge gas, respectively; and (b) a
depositing output face separated a distance from the substrate and
comprising a plurality of substantially parallel elongated output
openings for each of the first reactive gaseous material, the
second reactive gaseous material, and the inert purge gas, wherein
the delivery head is designed to deliver the first reactive gaseous
material, the second reactive gaseous material, and the inert purge
gas simultaneously from the elongated output openings in the
depositing output face; (C) an exit section; (D) means for moving
the substrate in a unidirectional passage through the coating
section; and (E) means for maintaining a substantially uniform
distance between the depositing output face of the delivery head
and a surface of the substrate during deposition of the thin film,
wherein the delivery head in the coating section is designed to
provide flows of one or more of the gaseous materials to the
substrate surface for thin film deposition that also provides at
least part of a force separating the depositing output face of the
delivery head from the surface of the substrate, wherein optionally
the entrance section and/or the exit section each comprises a
non-depositing output face having a plurality of non-depositing
output openings designed to provide gas flow of non-reactive gas to
the surface of the substrate during at least part of the passage
through the deposition system.
20. The process of claim 15 wherein the surface of the substrate is
exposed to a gas flow in a channel for less than 100 milliseconds
and the relative movement of the substrate to the deposition device
is at a speed at least 0.1 cm/sec.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Reference is made to commonly assigned U.S. patent
application Ser. No. 11/616,536 filed Dec. 27, 2006, entitled "OLED
WITH PROTECTIVE ELECTRODE" by Ronald Steven Cok, U.S. application
Ser. No. 11/392,007, filed Mar. 29, 2006 by Levy and entitled,
"PROCESS FOR ATOMIC LAYER DEPOSITION," U.S. application Ser. No.
11/392,006, filed Mar. 29, 2006 by Levy and entitled "APPARATUS FOR
ATOMIC LAYER DEPOSITION," U.S. application Ser. No. 11/620,738,
filed Jan. 8, 2007 by Levy and entitled "DELIVERY DEVICE FOR
DEPOSITION," U.S. application Ser. No. 11/620,740, filed Jan. 8,
2007 by Nelson et al. and entitled "DELIVERY DEVICE COMPRISING GAS
DIFFUSER FOR THIN FILM DEPOSITION," U.S. application Ser. No.
11/620,744, filed Jan. 8, 2007 by Levy and entitled, "DEPOSITION
SYSTEM AND METHOD USING A DELIVERY HEAD SEPARATED FROM A SUBSTRATE
BY GAS PRESSURE," U.S. application Ser. No. 11/627,525 (docket
93187), filed Jan. 26, 2007 by Peter Cowdery-Corvan et al. and
entitled, "PROCESS FOR ATOMIC LAYER DEPOSITION," U.S. application
Ser. No. ______ (docket 94077), filed concurrently herewith by Kerr
et al. and entitled, "DEPOSITION SYSTEM FOR THIN FILM FORMATION,"
U.S. application Ser. No. ______ (docket 94217), filed concurrently
herewith by Kerr et al. and entitled "DELIVERY DEVICE FOR
DEPOSITION," U.S. application Ser. No. ______ (docket 94079), filed
concurrently herewith by Levy et al. and entitled, "SYSTEM FOR THIN
FILM DEPOSITION UTILIZING COMPENSATING FORCES," U.S. application
Ser. No. ______ (docket 93882), filed concurrently herewith by Levy
et al. and entitled, "DEPOSITION SYSTEM FOR THIN FILM DEPOSITION,"
and U.S. application Ser. No. ______ (docket 94285), filed
concurrently herewith by Fedorovskaya et al. and entitled, "THIN
FILM ENCAPSULATION CONTAINING ZINC OXIDE." All the above-identified
applications incorporated by reference in their entirety.
FIELD OF THE INVENTION
[0002] This invention generally relates to the deposition of
thin-film materials and, more particularly, to a process for atomic
layer deposition onto a substrate using a deposition device. In
particular, the present invention relates to a process of making
films of metal-oxide materials for thin film encapsulation of OLED
devices.
BACKGROUND OF THE INVENTION
[0003] Organic light-emitting diodes (OLEDs) are a promising
technology for flat-panel displays and area illumination lamps. The
technology relies upon thin-film layers of organic materials coated
upon a substrate. OLED devices generally can have two formats known
as small-molecule devices such as disclosed in U.S. Pat. No.
4,476,292 and polymer OLED devices such as disclosed in U.S. Pat.
No. 5,247,190. Either type of OLED device may include, in sequence,
an anode, an organic EL element, and a cathode. The organic EL
element disposed between the anode and the cathode commonly
includes an organic hole-transporting layer (HTL), an emissive
layer (EL) and an organic electron-transporting layer (ETL). Holes
and electrons recombine and emit light in the EL layer. Tang et al.
(Appl. Phys. Lett., 51, 913 (1987), Journal of Applied Physics, 65,
3610 (1989) and U.S. Pat. No. 4,769,292) demonstrated highly
efficient OLEDs using such a layer structure. Since then, numerous
OLEDs with alternative layer structures, including polymeric
materials, have been disclosed and device performance has been
improved. However, the materials comprising the organic EL element
are sensitive and, in particular, are easily destroyed by moisture
and high temperatures (for example greater than 140 degrees
C.).
[0004] Transparent conductive electrodes typically employ
sputter-deposited conductive metal oxides such as indium tin oxide.
The described sputter deposited electrode layers, as well as
underlying layers, typically are not sufficiently impermeable to
environmental contaminants when employed as the transparent top
electrode in a top-emitting device, necessitating the use of
additional encapsulating overcoat layers or sealed transparent
glass covers, thereby exacerbating problems with light trapping
and/or increased costs for such devices.
[0005] It is well known that OLED materials are subject to
degradation in the presence of environmental contaminants, in
particular moisture. Organic light-emitting diode (OLED) display
devices typically require humidity levels below about 1000 parts
per million (ppm) to prevent premature degradation of device
performance within a specified operating and/or storage life of the
device. Control of the environment to this range of humidity levels
within a packaged device is typically achieved, as mentioned above,
by encapsulating the device with an encapsulating layer and/or by
sealing the device, and/or providing a desiccant within a cover.
Desiccants such as, for example, metal oxides, alkaline earth metal
oxides, sulfates, metal halides, and perchlorates are used to
maintain the humidity level below the above-specified level. See,
for example, U.S. Pat. No. 6,226,890 issued May 8, 2001 to Boroson
et al. describing desiccant materials for moisture-sensitive
electronic devices. Such desiccating materials are typically
located around the periphery of an OLED device or over the OLED
device itself.
[0006] In alternative approaches, an OLED device is encapsulated
using thin multilayer coatings of moisture-resistant material. For
example, layers of inorganic materials such as metals or metal
oxides separated by layers of an organic polymer may be used. Such
coatings have been described in, for example, U.S. Pat. Nos.
6,268,695; 6,413,645; 6,522,067, and US Patent Publication No.
2006/0246811, the latter reference hereby incorporated by reference
in its entirety.
[0007] Such encapsulating layers may be deposited by various
techniques, including atomic layer deposition (ALD). One such
atomic layer deposition apparatus is further described in WO0182390
to Ghosh et al. entitled "THIN FILM ENCAPSULATION OF ORGANIC LIGHT
EMITTING DIODE DEVICES" describes the use of first and second thin
film encapsulation layers made of different materials wherein one
of the thin-film layers is deposited at 50 nm using atomic layer
deposition discussed below. According to this disclosure, a
separate protective layer is also employed, e.g., parylene. Such
thin multi layer coatings typically attempt to provide a moisture
permeation rate of less than 5.times.10.sup.-6 g/m.sup.2/day to
adequately protect the OLED materials. In contrast, typically
polymeric materials have a moisture permeation rate of
approximately 0.1 gm/m.sup.2/day and cannot adequately protect the
OLED materials without additional moisture blocking layers. With
the addition of inorganic moisture blocking layers, 0.01
g/m.sup.2/day may be achieved and it has been reported that the use
of relatively thick polymer smoothing layers with inorganic layers
may provide the needed protection. Thick inorganic layers, for
example 5 microns or more of ITO or ZnSe, applied by conventional
deposition techniques such as sputtering or vacuum evaporation may
also provide adequate protection, but thinner conventionally coated
layers may only provide protection of 0.01 gm/m.sup.2/day. US
2007/0099356 to Park et al. entitled "FLAT PANEL DISPLAY DEVICE AND
METHOD OF MANUFACTURING THE SAME" similarly describes a method for
thin film encapsulation of flat panel displays using atomic layer
deposition.
[0008] WO2004105149 TO Carcia et al. entitled "BARRIER FILMS FOR
PLASTIC SUBSTRATES FABRICATED BY ATOMIC LAYER DEPOSITION" published
Dec. 2, 2004 describes gas permeation barriers that can be
deposited on plastic or glass substrates by atomic layer
deposition. Atomic Layer Deposition is also known as Atomic Layer
Epitaxy (ALE) or atomic layer CVD (ALCVD), and reference to ALD
herein is intended to refer to all such equivalent processes. The
use of the ALD coatings can reduce permeation by many orders of
magnitude at thicknesses of tens of nanometers with low
concentrations of coating defects. These thin coatings preserve the
flexibility and transparency of the plastic substrate. Such
articles are useful in container, electrical, and electronic
applications. However, such protective layers also cause additional
problems with light trapping in the layers since they may be of
lower index than the light-emitting organic layers.
[0009] Among the techniques widely used for thin-film deposition is
Chemical Vapor Deposition (CVD) that uses chemically reactive
molecules that react in a reaction chamber to deposit a desired
film on a substrate. Molecular precursors useful for CVD
applications comprise elemental (atomic) constituents of the film
to be deposited and typically also include additional elements. CVD
precursors are volatile molecules that are delivered, in a gaseous
phase, to a chamber in order to react at the substrate, forming the
thin film thereon. The chemical reaction deposits a thin film with
a desired film thickness.
[0010] Common to most CVD techniques is the need for application of
a well-controlled flux of one or more molecular precursors into the
CVD reactor. A substrate is kept at a well-controlled temperature
under controlled pressure conditions to promote chemical reaction
between these molecular precursors, concurrent with efficient
removal of byproducts. Obtaining optimum CVD performance requires
the ability to achieve and sustain steady-state conditions of gas
flow, temperature, and pressure throughout the process, and the
ability to minimize or eliminate transients.
[0011] There is interest in utilizing processes for deposition that
do not involve the expense associated with vacuum processing. In
typical vacuum processing, a large metal chamber and sophisticated
vacuum pumping systems are required in order to provide the
necessary environment. These items increase the capital cost of
systems and preclude the easy use of continuous web based
systems.
[0012] Various processes for making metal oxide films have been
disclosed, both high temperature and low temperature processes,
including radio frequency magnetron sputtering or modified reactive
planar magnetron sputtering. ALD can be used as a fabrication step
for forming a number of types of thin film electronic devices,
including semiconductor devices and supporting electronic
components such as resistors and capacitors, insulators, bus lines,
and other conductive structures. ALD is particularly suited for
forming thin layers of metal oxides in the components of electronic
devices. General classes of functional materials that can be
deposited with ALD include conductors, dielectrics or insulators,
and semiconductors.
[0013] Advantageously, ALD steps are self-terminating and can
deposit precisely one atomic layer when conducted up to or beyond
self-termination exposure times. An atomic layer typically ranges
from about 0.1 to about 0.5 molecular monolayers, with typical
dimensions on the order of no more than a few Angstroms. In ALD,
deposition of an atomic layer is the outcome of a chemical reaction
between a reactive molecular precursor and the substrate. In each
separate ALD reaction-deposition step, the net reaction deposits
the desired atomic layer and substantially eliminates "extra" atoms
originally included in the molecular precursor. In its most pure
form, ALD involves the adsorption and reaction of each of the
precursors in the complete absence of the other precursor or
precursors of the reaction. In practice in any process it is
difficult to avoid some direct reaction of the different precursors
leading to a small amount of chemical vapor deposition reaction.
The goal of any process claiming to perform ALD is to obtain device
performance and attributes commensurate with an ALD process while
recognizing that a small amount of CVD reaction can be
tolerated.
[0014] In ALD applications, typically two molecular precursors are
introduced into the ALD reactor in separate stages. For example, a
metal precursor molecule, ML.sub.x, comprises a metal element, M
that is bonded to an atomic or molecular ligand, L. For example, M
could be, but would not be restricted to, Al, W, Ta, Si, Zn, etc.
The metal precursor reacts with the substrate when the substrate
surface is prepared to react directly with the molecular precursor.
For example, the substrate surface typically is prepared to include
hydrogen-containing ligands, AH or the like, that are reactive with
the metal precursor. Sulfur (S), oxygen (O), and Nitrogen (N) are
some typical A species. The gaseous precursor molecule effectively
reacts with all of the ligands on the substrate surface, resulting
in deposition of a single atomic layer of the metal:
substrate-AH+ML.sub.x.fwdarw.substrate-AML.sub.x-1+HL (1)
where HL is a reaction by-product. During the reaction, the initial
surface ligands, AH, are consumed, and the surface becomes covered
with AML.sub.x-1 ligands, which cannot further react with metal
precursor ML.sub.x. Therefore, the reaction self-terminates when
all of the initial AH ligands on the surface are replaced with
AML.sub.x-1 species. The reaction stage is typically followed by an
inert-gas purge stage that eliminates the excess metal precursor
and the HL by-product species from the chamber prior to the
separate introduction of the other precursor.
[0015] A second molecular precursor then is used to restore the
surface reactivity of the substrate towards the metal precursor.
This is done, for example, by removing the L ligands and
re-depositing AH ligands. In this case, the second precursor
typically comprises the desired (usually nonmetallic) element A
(i.e., O, N, S), and hydrogen (i.e., H.sub.2O, NH.sub.3, H.sub.2S).
The next reaction is as follows:
substrate-A-ML+AH.sub.Y.fwdarw.substrate-A-M-AH+HL (2)
[0016] This converts the surface back to its AH-covered state.
(Here, for the sake of simplicity, the chemical reactions are not
balanced.) The desired additional element, A, is incorporated into
the film and the undesired ligands, L, are eliminated as volatile
by-products. Once again, the reaction consumes the reactive sites
(this time, the L terminated sites) and self-terminates when the
reactive sites on the substrate are entirely depleted. The second
molecular precursor then is removed from the deposition chamber by
flowing inert purge-gas in a second purge stage.
[0017] In summary, then, an ALD process requires alternating in
sequence the flux of chemicals to the substrate. The representative
ALD process, as discussed above, is a cycle having four different
operational stages:
[0018] 1. ML.sub.x reaction;
[0019] 2. ML.sub.x purge;
[0020] 3. AH.sub.y reaction; and
[0021] 4. AH.sub.y purge, and then back to stage 1.
[0022] This repeated sequence of alternating surface reactions and
precursor-removal that restores the substrate surface to its
initial reactive state, with intervening purge operations, is a
typical ALD deposition cycle. A key feature of ALD operation is the
restoration of the substrate to its initial surface chemistry
condition. Using this repeated set of steps, a film can be layered
onto the substrate in equal metered layers that are all identical
in chemical kinetics, deposition per cycle, composition, and
thickness.
[0023] Self-saturating surface reactions make ALD insensitive to
transport non-uniformities, which might otherwise impair surface
uniformity, due either to engineering tolerances and the
limitations of the flow process or related to surface topography
(that is, deposition into three dimensional, high aspect ratio
structures). As a general rule, a non-uniform flux of chemicals in
a reactive process generally results in different completion times
at different areas.
[0024] However, with ALD, each of the reactions is allowed to
complete on the entire substrate surface. Thus, differences in
completion kinetics impose no penalty on uniformity. This is
because the areas that are first to complete the reaction
self-terminate the reaction; other areas are able to continue until
the full treated surface undergoes the intended reaction.
[0025] Typically, an ALD process deposits about 0.1-0.2 nm of a
film in a single ALD cycle (with numbered steps 1 through 4 as
listed earlier). A useful and economically feasible cycle time must
be achieved in order to provide a uniform film thickness in a range
of from about 3 nm to 300 nm for many or most semiconductor
applications, and even thicker films for other applications.
Industry throughput standards dictate that substrates be processed
in 2 minutes to 3 minutes, which means that ALD cycle times must be
in a range from about 0.6 seconds to about 6 seconds.
[0026] An ALD process must be able to execute this sequencing
efficiently and reliably for many cycles in order to allow
cost-effective coating of many substrates. In an effort to minimize
the time that an ALD reaction needs to reach self-termination, at
any given reaction temperature, one approach has been to maximize
the flux of chemicals flowing into the ALD reactor, using a
so-called "pulsing" process. In the pulsed ALD process, a substrate
sits in a chamber and is exposed to the above sequence of gases by
allowing a first gas to enter the chamber, followed by a pumping
cycle to remove that gas, followed by the introduction of a second
gas to the chamber, followed by a pumping cycle to remove the
second gas. This sequence can be repeated at any frequency and
variations in gas type and/or concentration. The net effect is that
the entire chamber experiences a variation in gas composition with
time, and thus this type of ALD can be referred to as time
dependent ALD. The vast majority of existing ALD processes are time
dependent ALD.
[0027] In order to maximize the flux of chemicals into the ALD
reactor, it is advantageous to introduce the molecular precursors
into the ALD reactor with minimum dilution of inert gas and at high
pressures. However, these measures work against the need to achieve
short cycle times and the rapid removal of these molecular
precursors from the ALD reactor. Rapid removal in turn dictates
that gas residence time in the ALD reactor be minimized.
[0028] Existing ALD approaches have been compromised with the
trade-off between the need to shorten reaction times and improve
chemical utilization efficiency, and on the other hand, the need to
minimize purge-gas residence and chemical removal times. One
approach to overcome the inherent limitations of time depended ALD
systems is to provide each reactant gas continuously and to move
the substrate through each gas in succession. In these systems a
relatively constant gas composition exists, but is located to
specific areas or spaces of the processing system. Therefore, these
systems will be referred to as spatially dependent ALD systems.
[0029] For example, U.S. Pat. No. 6,821,563 entitled "GAS
DISTRIBUTION SYSTEM FOR CYCLICAL LAYER DEPOSITION" to Yudovsky
describes a spatially dependent ALD processing system, under
vacuum, having separate gas ports for precursor and purge gases,
alternating with vacuum pump ports between each gas port. Each gas
port directs its stream of gas vertically downward toward a
substrate. The separate gas flows are separated by walls or
partitions, with vacuum pumps for evacuating gas on both sides of
each gas stream. A lower portion of each partition extends close to
the substrate, for example, about 0.5 mm or greater from the
substrate surface. In this manner, the lower portions of the
partitions are separated from the substrate surface by a distance
sufficient to allow the gas streams to flow around the lower
portions toward the vacuum ports after the gas streams react with
the substrate surface.
[0030] A rotary turntable or other transport device is provided for
holding one or more substrate wafers. With this arrangement, the
substrate is shuttled beneath the different gas streams, effecting
ALD deposition thereby. In one embodiment, the substrate is moved
in a linear path through a chamber, in which the substrate is
passed back and forth a number of times.
[0031] Another approach using continuous gas flow spatially
dependent ALD is shown in U.S. Pat. No. 4,413,022 entitled "METHOD
FOR PERFORMING GROWTH OF COMPOUND THIN FILMS" to Suntola et al. A
gas flow array is provided with alternating source gas openings,
carrier gas openings, and vacuum exhaust openings. Reciprocating
motion of the substrate over the array effects ALD deposition,
again, without the need for pulsed operation. In the embodiment of
FIGS. 13 and 14, in particular, sequential interactions between a
substrate surface and reactive vapors are made by a reciprocating
motion of the substrate over a fixed array of source openings.
Diffusion barriers are formed by a carrier gas opening between
exhaust openings. Suntola et al. state that operation with such an
embodiment is possible even at atmospheric pressure, although
little or no details of the process, or examples, are provided.
[0032] While processes such as those described in the '563 Yudovsky
and '022 Suntola et al. patents may avoid some of the difficulties
inherent to pulsed gas approaches, these processes have other
drawbacks. For example, it would be very difficult to maintain a
uniform vacuum at different points in an array and to maintain
synchronous gas flow and vacuum at complementary pressures, thus
compromising the uniformity of gas flux that is provided to the
substrate surface. Neither the gas flow delivery unit of the '563
Yudovsky patent nor the gas flow array of the '022 Suntola et al.
patent can be used in closer proximity to the substrate than about
0.5 mm.
[0033] U.S. Patent Publication No. 2005/0084610 to Selitser
discloses an atmospheric pressure atomic layer chemical vapor
deposition process. Selitser states that extraordinary increases in
reaction rates are obtained by changing the operating pressure to
atmospheric pressure, which will involve orders of magnitude
increase in the concentration of reactants, with consequent
enhancement of surface reactant rates. The embodiments of Selitser
involve separate chambers for each stage of the process, although
FIG. 10 shows an embodiment in which chamber walls are removed. A
series of separated injectors are spaced around a rotating circular
substrate holder track. Each injector incorporates independently
operated reactant, purging, and exhaust gas manifolds and controls
and acts as one complete mono-layer deposition and reactant purge
cycle for each substrate as is passes there under in the process.
Little or no specific details of the gas injectors or manifolds are
described by Selitser, although it is stated that spacing of the
injectors is selected so that cross-contamination from adjacent
injectors is prevented by purging gas flows and exhaust manifolds
incorporated in each injector.
[0034] A spatially dependent ALD process can be accomplished with
other apparatus or systems described in more detail in commonly
assigned U.S. application Ser. No. 11/392,007, U.S. application
Ser. No. 11/392,006, U.S. application Ser. No. 11/620,744, and U.S.
application Ser. No. 11/620,740. All these identified applications
hereby incorporated by reference in their entirety. These systems
attempt to overcome one of the difficult aspects of a spatial ALD
system, which is undesired intermixing of the continuously flowing
mutually reactive gases. In particular, U.S. application Ser. No.
11/392,007 employs a novel transverse flow pattern to prevent
intermixing, while U.S. application Ser. No. 11/620,744 and U.S.
application Ser. No. 11/620,740 employ a coating head partially
levitated by the pressure of the reactive gases of the process to
accomplish improved gas separation.
[0035] Despite the usefulness and ease of use of these spatially
dependent ALD systems, they continue to be less capable than time
dependent ALD systems in terms of separation of the mutually
reactive gases. Thus, to render them industrially useful,
chemistries must be considered that are more robust to avoid
problems associated with gas intermixing.
[0036] Thus, there remains still a need to provide a spatially
dependent ALD system to make metal-oxide thin film encapsulating
films.
SUMMARY OF THE INVENTION
[0037] The present invention relates to a process of making a thin
film encapsulation package for an OLED device by depositing a thin
film material on an OLED device to be encapsulated, comprising
simultaneously directing a series of gas flows along substantially
parallel elongated output openings, wherein the series of gas flows
comprises, in order, at least a first reactive gaseous material, an
inert purge gas, and a second reactive gaseous material, optionally
repeated a plurality of times, wherein the first reactive gaseous
material is capable of reacting with a substrate surface treated
with the second reactive gaseous material to form an encapsulating
thin film, wherein the first reactive gaseous material is a
volatile organo-metal precursor compound, wherein the process is
carried out substantially at or above atmospheric pressure, and
wherein the temperature of the substrate during deposition is under
250.degree. C.
[0038] During the process, the substrate or deposition device for
the gaseous materials, or both, is capable of providing relative
movement between the output face of the deposition device and the
substrate while maintaining close proximity.
[0039] In a preferred embodiment, the process can be operated with
continuous movement of a substrate being subjected to thin film
deposition, wherein the process is capable of conveying the support
on or as a web past the deposition device, preferably in an
unsealed environment to ambient at substantially atmospheric
pressure.
[0040] It is an advantage of the present invention that it provides
an advantageous process for atomic layer deposition of a
metal-oxide-based layers onto a substrate, well suited to a number
of different types of substrates and deposition environments.
[0041] It is yet a further advantage of the present invention that
it is adaptable for deposition on a web or other moving substrate,
including deposition onto a large area substrate.
[0042] It is a further advantage of the present invention that it
allows operation, in preferred embodiments, under atmospheric
pressure conditions.
[0043] It is still a further advantage of the present invention
that it can be employed in low temperature processes at atmospheric
pressures, which processes may be practice in an unsealed
environment, open to ambient atmosphere.
[0044] The objects, features, and advantages of the present
invention will become apparent to those skilled in the art upon a
reading of the following detailed description when taken in
conjunction with the drawings wherein there is shown and described
an illustrative embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] While the specification concludes with claims particularly
pointing out and distinctly claiming the subject matter of the
present invention, it is believed that the invention will be better
understood from the following description when taken in conjunction
with the accompanying drawings, wherein:
[0046] FIG. 1 is a flow chart describing the steps of the present
process;
[0047] FIG. 2 is a cross-sectional side view of one embodiment of a
deposition device for atomic layer deposition that can be used in
the present process;
[0048] FIG. 3 is a cross-sectional side view of an embodiment, for
one exemplary system of gaseous materials, of the distribution of
gaseous materials to a substrate that is subjected to thin film
deposition;
[0049] FIGS. 4A and 4B are cross-sectional side views of one
embodiment of the distribution of a system of gaseous materials,
schematically showing the accompanying deposition operation;
[0050] FIG. 5 is a perspective view, from the output face side, of
a portion of one embodiment of a deposition device, showing the
orientation of output channels relative to the substrate and
reciprocating motion, that can be used for deposition on the
substrate;
[0051] FIG. 6 is a perspective view as in FIG. 5, showing one
exemplary arrangement of gas flow in the deposition device;
[0052] FIGS. 7A, 7B, 7C, and 7D are cross-sectional views taken
orthogonally to the cross-sectional views of previous FIGS. 2-4B,
showing gas flow directions for output channels in various
embodiments;
[0053] FIGS. 8A and 8B are cross-sectional views showing the impact
of reduced distance from the output face, of a deposition device
for providing gaseous materials, to the substrate surface;
[0054] FIG. 9 is a plan view of the output face of a deposition
device such as shown in FIG. 3 that can be used in the present
process, showing movement of gaseous materials through an
arrangement of output channels according to one embodiment of the
invention;
[0055] FIG. 10 is a perspective view of one embodiment of a
deposition device formed from stacked plates that can be used in
the present process;
[0056] FIGS. 11A and 11B are exploded views of the construction of
a deposition device that employs the stacked-plate structure shown
in FIG. 10, the exploded views showing two different output
channels for different gases used in the process;
[0057] FIG. 12 is a perspective view showing an embodiment using an
enveloping shroud of inert gas directed along the perimeter of the
deposition device;
[0058] FIG. 13 is a schematic diagram showing an alternative motion
pattern for reciprocating and orthogonal movement;
[0059] FIG. 14 is a block diagram of one embodiment of a deposition
system that uses the process according to the present
invention;
[0060] FIG. 15 is a block diagram showing one embodiment of a
deposition system applied to a moving web in accordance with the
present process;
[0061] FIG. 16 is a block diagram showing another embodiment of
deposition system applied to a moving web in accordance with the
present process, with the deposition device stationary;
[0062] FIG. 17 is a cross-sectional side view of one embodiment of
a deposition device with an output face having curvature that can
be used in the present process;
[0063] FIG. 18 is a block diagram of the source materials for a
thin film deposition process according to the Examples;
[0064] FIG. 19 is a cross-sectional side view of the a deposition
device used in the present process, showing the arrangement of
gaseous materials provided to a substrate that is subjected to thin
film deposition process of the Examples;
[0065] FIG. 20 is a cross-sectional view of a top-emitting OLED
device according to an embodiment of the present invention; and
[0066] FIG. 21 is a cross-sectional view of an OLED device having
color filters according to an alternative embodiment of the present
invention;
DETAILED DESCRIPTION OF THE INVENTION
[0067] As indicated above, the present process is directed to
making a thin film encapsulation package for an OLED device by
depositing a thin film material on an OLED device to be
encapsulated with at least one encapsulating thin film.
[0068] In one embodiment, the encapsulation package can comprise a
single layer of a single inorganic compound. In another preferred
embodiment, the thin film encapsulation package comprises either
(a) at least one first layer of a first inorganic compound and at
least one second layer of a second inorganic compound, or (b) a
layer that is a mixture of a first inorganic compound and a second
inorganic compound. The first inorganic compound and the second
inorganic compound can be independently selected from an oxide,
nitride, sulfide and phosphide. Preferably, at least one of the
first and second compound is an oxide or nitride, and more
preferably at least one of the first and the second inorganic
compound is aluminum oxide. More generally, the first and second
inorganic compound can independently comprise an element that is
independently selected from elements in Group 3A, 3B, 4A, and 4B of
the Periodic Table. In a particularly preferred embodiment, the
first and second inorganic compound comprises an element that is
independently selected from the group consisting of zinc, aluminum,
titanium, hafnium, silicon, zirconium, yttrium, and indium and
there are a plurality of first encapsulating thin films and/or
plurality of second encapsulating thin films in which the first and
second encapsulating thin films alternate in a stack.
[0069] Volatile compounds are defined as compounds that can exist
to some extent in the vapor phase at room temperature, so that they
may be delivered to a reaction chamber in the form of a gas. In
order for such a gas to contain sufficient volatile materials to
usefully affect the deposition process, the volatile compound must
have a vapor pressure at room temperature of greater than 0.1 mmHg,
preferably greater than 1 mmHg. Such dopants are preferably present
in the final semiconductor in the amount of 0.001% to 5%, more
preferably 0.01% to 1%.
[0070] For the description that follows, the term "gas" or "gaseous
material" is used in a broad sense to encompass any of a range of
vaporized or gaseous elements, compounds, or materials. Other terms
used herein, such as: reactant, precursor, vacuum, and inert gas,
for example, all have their conventional meanings as would be well
understood by those skilled in the materials deposition art. The
figures provided are not drawn to scale but are intended to show
overall function and the structural arrangement of some embodiments
of the present invention.
[0071] The process of the present invention offers a significant
departure from conventional approaches to ALD, employing a system
for delivery of gaseous materials to a substrate surface that can
be adaptable to deposition on larger and web-based substrates and
capable of achieving a highly uniform thin-film deposition at
improved throughput speeds. The process of the present invention
employs a continuous spatially dependent ALD (as opposed to pulsed
or time dependent ALD) gaseous material distribution. The process
of the present invention allows operation at atmospheric or
near-atmospheric pressures and is capable of operating in an
unsealed or open-air environment.
[0072] FIG. 1 is a generalized step diagram of one embodiment of a
process for making a film of an encapsulation layer according to an
embodiment of the present invention, in which two reactive gases
are used, a first molecular precursor and a second molecular
precursor. Gases are supplied from a gas source and can be
delivered to the substrate, for example, via a deposition device.
Metering and valving apparatus for providing gaseous materials to
the a deposition device can be used.
[0073] As shown in Step 1, a continuous supply of gaseous materials
for the system is provided for depositing a thin film of material
on a substrate. The Steps in Sequence 15 are sequentially applied.
In Step 2, with respect to a given area of the substrate (referred
to as the channel area), a first molecular precursor or reactive
gaseous material is directed to flow in a first channel over the
channel area of the substrate and reacts therewith. In Step 3
relative movement of the substrate and the multi-channel flows in
the system occurs, which sets the stage for Step 4, in which second
channel (purge) flow with inert gas occurs over the given channel
area. Then, in Step 5, relative movement of the substrate and the
multi-channel flows sets the stage for Step 6, in which the given
channel area is subjected to atomic layer deposition in which a
second molecular precursor now (in this particular embodiment,
transversely and substantially parallel to the surface of the
substrate) over the given channel area of the substrate and reacts
with the previous layer on the substrate to produce (theoretically)
a monolayer of a desired material.
[0074] In Step 7, relative movement of the substrate and the
multi-channel flows then sets the stage for Step 8 in which again
an inert gas is used, this time to sweep excess second molecular
precursor from the given channel area from the previous Step 6. In
Step 9, relative movement of the substrate and the multi-channels
occurs again, which sets the stage for a repeat sequence, back to
Step 2. The cycle is repeated as many times as is necessary to
establish a desired film. In the present embodiment of the process,
the steps are repeated with respect to a given channel area of the
substrate, corresponding to the area covered by a flow channel.
Meanwhile the various channels are being supplied with the
necessary gaseous materials in Step 1. Simultaneous with the
sequence of box 15 in FIG. 1, other adjacent channel areas are
being processed, which results in Multiple channel flows in
parallel, as indicated in overall Step 11. Parallel flow can be
either substantially orthogonal or substantially parallel to the
output face of the deposition device.
[0075] The primary purpose of the second molecular precursor is to
condition the substrate surface back toward reactivity with the
first molecular precursor. The second molecular precursor also
provides material from the molecular gas to combine with metal at
the surface, forming an oxide with the freshly deposited
metal-containing precursor.
[0076] This particular embodiment does not need to use a vacuum
purge to remove a molecular precursor after applying it to the
substrate. Purge steps are expected by most researchers to be the
most significant throughput-limiting step in ALD processes.
[0077] Assuming that, for the two reactant gases in FIG. 1, AX and
BY are used, for example. When the reaction gas AX flow is supplied
and flowed over a given substrate area, atoms of the reaction gas
AX are chemically adsorbed on a substrate, resulting in a layer of
A and a surface of ligand X (associative chemisorptions) (Step 2).
Then, the remaining reaction gas AX is purged with an inert gas
(Step 4). Then, the flow of reaction gas BY, and a chemical
reaction between AX (surface) and BY (gas) occurs, resulting in a
molecular layer of AB on the substrate (dissociative
chemisorptions) (Step 6). The remaining gas BY and by-products of
the reaction are purged (Step 8). The thickness of the thin film
can be increased by repeating the process cycle (steps 2-9) many
times.
[0078] Because the film can be deposited one monolayer at a time it
tends to be conformal and have uniform thickness.
[0079] It will be apparent to the skilled artisan that alloys of
two, three, or more metals may be deposited, compounds may be
deposited with two, three, or more constituents, and such things as
graded films and nano-laminates may be produced as well.
[0080] These variations are simply variants using particular
embodiments of the invention in alternating cycles. There are many
other variations within the spirit and scope of the invention, so
the invention is limited only by the claims that follow.
[0081] For various volatile metal-containing precursors, precursor
combinations, and reactants useful in ALD thin film processes,
reference is made to the Handbook of Thin Film Process Technology,
Vol. 1, edited by Glocker and Shah, Institute of Physics (IOP)
Publishing, Philadelphia 1995, pages B1.5:1 to B1.5:16, hereby
incorporated by reference; and Handbook of Thin Film Materials,
edited by Nalwa, Vol. 1, pages 103 to 159, hereby incorporated by
reference, including Table V1.5.1 of the former reference.
[0082] Although oxide substrates provide groups for ALD deposition,
plastic substrates can be used by suitable surface treatment.
[0083] Referring now to FIG. 2, there is shown a cross-sectional
side view of one embodiment of a deposition device 10 that can be
used in the present process for atomic layer deposition of an
encapsulating thin film onto a substrate 20 according to the
present invention. Deposition device 10 has a gas inlet port 14 for
accepting a first gaseous material, a gas inlet port 16 for
accepting a second gaseous material, and a gas inlet port 18 for
accepting a third gaseous material. These gases are emitted at an
output face 36 via output channels 12, having a structural
arrangement described subsequently. The arrows in FIG. 2 and
subsequent FIGS. 3-4B refer to the diffusive transport of the
gaseous material, and not the flow, received from an output
channel. In this particular embodiment, the flow is substantially
directed out of the page of the figure, as described further
below.
[0084] In one embodiment, gas inlet ports 14 and 16 are adapted to
accept first and second gases that react sequentially on the
substrate surface to effect ALD deposition, and gas inlet port 18
receives a purge gas that is inert with respect to the first and
second gases. Deposition device 10 is spaced a distance D from
substrate 20, provided on a substrate support, as described in more
detail subsequently. Reciprocating motion can be provided between
substrate 20 and deposition device 10, either by movement of
substrate 20, by movement of deposition device 10, or by movement
of both substrate 20 and deposition device 10. In the particular
embodiment shown in FIG. 2, substrate 20 is moved across output
face 36 in reciprocating fashion, as indicated by the arrow R and
by phantom outlines to the right and left of substrate 20 in FIG.
2. It should be noted that reciprocating motion is not always
required for thin-film deposition using deposition device 10. Other
types of relative motion between substrate 20 and deposition device
10 could also be provided, such as movement of either substrate 20
or deposition device 10 in one or more directions, as described in
more detail subsequently.
[0085] The cross-sectional view of FIG. 3 shows gas flows emitted
over a portion of output face 36 of deposition device 10. In this
particular arrangement, each output channel 12, separated by
partitions 22, is in gaseous flow communication with one of gas
inlet ports 14, 16 or 18 seen in FIG. 2. Each output channel 12
delivers typically a first reactant gaseous material O, or a second
reactant gaseous material M, or a third inert gaseous material
I.
[0086] FIG. 3 shows a relatively basic or simple arrangement of
gases. It is envisioned that a plurality of non-metal deposition
precursors (like material 0) or a plurality of metal-containing
precursor materials (like material M) may be delivered sequentially
at various ports in a thin-film single deposition. Alternately, a
mixture of reactant gases, for example, a mixture of metal
precursor materials or a mixture of metal and non-metal precursors
may be applied at a single output channel when making complex thin
film materials, for example, having alternate layers of metals or
having lesser amounts of dopants admixed in a metal oxide material.
The inter-stream labeled I separates any reactant channels in which
the gases are likely to react with each other. First and second
reactant gaseous materials O and M react with each other to effect
ALD deposition, but neither reactant gaseous material O nor M
reacts with inert gaseous material I. The nomenclature used in FIG.
3 and following suggests some typical types of reactant gases. For
example, first reactant gaseous material O could be an oxidizing
gaseous material; second reactant gaseous material M could be a
metal-containing compound. Inert gaseous material I could be
nitrogen, argon, helium, or other gases commonly used as purge
gases in ALD processes. Inert gaseous material I is inert with
respect to first or second reactant gaseous materials O and M.
Reaction between first and second reactant gaseous materials could
form a metal oxide or other binary compound. Reactions between more
than two reactant gaseous materials could form a ternary compound,
for example, ZnAlO.
[0087] The cross-sectional views of FIGS. 4A and 4B show, in
simplified schematic form, the ALD coating operation performed as
substrate 20 passes along output face 36 of deposition device 10
when delivering reactant gaseous materials O and M. In FIG. 4A, the
surface of substrate 20 first receives an oxidizing material from
output channels 12 designated as delivering first reactant gaseous
material O. The surface of the substrate now contains a partially
reacted form of material O, which is susceptible to reaction with
material M. Then, as substrate 20 passes into the path of the metal
compound of second reactant gaseous material M, the reaction with M
takes place, forming a metallic oxide or some other thin film
material that can be formed from two reactant gaseous
materials.
[0088] As FIGS. 4A and 4B show, inert gaseous material I is
provided in every alternate output channel 12, between the flows of
first and second reactant gaseous materials O and M. Sequential
output channels 12 are adjacent, that is, share a common boundary,
formed by partitions 22 in the embodiments shown. Here, output
channels 12 are defined and separated from each other by partitions
22 that extend at a perpendicular to the surface of substrate
20.
[0089] As mentioned above, in this particular embodiment, there are
no vacuum channels interspersed between the output channels 12,
that is, no vacuum channels on either side of a channel delivering
gaseous materials to drawn the gaseous materials around the
partitions. This advantageous, compact arrangement is possible
because of the innovative gas flow that is used. Unlike gas
delivery arrays of earlier processes that apply substantially
vertical (that is, perpendicular) gas flows against the substrate
and must then draw off spent gases in the opposite vertical
direction, deposition device 10 directs a gas flow (preferably
substantially laminar in one embodiment) along the surface for each
reactant and inert gas and handles spent gases and reaction
by-products in a different manner, as described subsequently. The
gas flow used in the present invention is directed along and
generally parallel to the plane of the substrate surface. In other
words, the flow of gases is substantially transverse to the plane
of a substrate rather than perpendicular to the substrate being
treated.
[0090] FIGS. 5 and 6 show perspective views of one embodiment of a
deposition device 10 that can be used in the present process, from
the output face 36 (that is, from the underside with respect to
FIGS. 2-4B). Partitions 22 that define and separate the adjacent
output channels 12 in this embodiment are represented as partially
cut away, to allow better visibility for the gas flows flowing from
gas outlet ports 24. FIGS. 5 and 6 also show reference x,y,z
coordinate axis assignments used in the figures of this disclosure.
Output channels 12 are substantially in parallel and extend in a
length direction that corresponds to the x coordinate axis.
Reciprocating motion of substrate 20, or motion relative to
substrate 20, is in they coordinate direction, using this
coordinate assignment.
[0091] FIG. 6 shows the gas flows F.sub.I, F.sub.O, and F.sub.M for
the various gaseous materials delivered from deposition device 10
with this embodiment. Gas flows F.sub.I, F.sub.O, and F.sub.M are
in the x-direction, that is, along the length of elongated output
channels 12.
[0092] The cross-sectional views of FIGS. 7A, 7B, 7C, and 7D are
taken orthogonally to the cross-sections of FIGS. 2-4B and show gas
flows in one direction from this view. Within each output channel
12, the corresponding gaseous material flows from a gas output port
24, shown in phantom in the views of FIGS. 7A, 7B, 7C, and 7D. In
the embodiment of FIG. 7A, gas flow F1 directs the gaseous material
along the length of output channel 12 and across substrate 20, as
was described with reference to FIGS. 5 and 6. Flow F1 continues
past the edge of deposition device 10 in this arrangement, flowing
outward into the environment or, if desirable, to a gas collection
manifold (not shown). FIG. 7B shows an alternative embodiment for
gas flow F2 in which output channel 12 also provides an exhaust
port 26 for redirection or drawing off of the gas flow. FIG. 7C
shows an alternative embodiment for gas flow F3, in which gas
output port 24 is centrally located within output channel 12 and
directs gaseous material in gas flows along the channel in both
directions. FIG. 7D shows an alternate embodiment for gas flow F4,
in which gas output port 24 is also centrally positioned, with
multiple exhaust ports 26 suitably placed near the extreme ends of
output channel 12. Although unidirectional flows are preferred,
some degree of mixing can occur and even may be beneficial to some
extent, depending on the flow rates and other circumstances
involved in a particular application.
[0093] A particular deposition device 10 may use output channels 12
configured using any one of the gas flow configurations or
combinations thereof, either the F1 flow of FIG. 7A, the F2 flow of
FIG. 7B, the F3 flow of FIG. 7C, the F4 flow of FIG. 7D, or some
other variation in which gaseous material is directed to flow
across substrate 20 along output channel 12, preferably in a
substantially laminar or smooth fashion with controlled mixing. In
one embodiment, one or more exhaust ports 26 are provided for each
output channel 12 that delivers a reactant gaseous material. For
example, referring to FIG. 6, output channels 12 for first and
second reactant gaseous materials, labeled O and M, are configured
with exhaust ports 26 to vent or draw off the reactant substances,
following the pattern of flow F2 (FIG. 7B). This allows some
recycling of materials and prevents undesirable mixing and reaction
near the end of the manifold. Output channels 12 for inert gaseous
material, labeled I, do not use exhaust ports 26 and thus follow
the pattern of flow F1 (FIG. 7A). Although laminar flows are
preferred in some embodiments, some degree of mixing can occur and
even may be beneficial to some extent, depending on the flow rates
and other circumstances involved in a particular application.
[0094] Exhaust port 26 is not a vacuum port, in the conventional
sense, but is simply provided to draw off the gaseous flow in its
corresponding output channel 12, thus facilitating a uniform gas
flow pattern within the channel. A negative draw, just slightly
less than the opposite of the gas pressure at gas output port 24,
can help to facilitate an orderly gas flow. The negative draw can,
for example, operate at a pressure of between 0.9 and 1.0
atmosphere, whereas a typical vacuum is, for example, below 0.1
atmosphere. An optional baffle 58, as shown in dotted outline in
FIGS. 7B and 7D may be provided to redirect the flow pattern into
exhaust port 26.
[0095] Because no gas flow around partition 22 to a vacuum exhaust
is needed, output face 36 can be positioned very closely, to within
about 1 mil (approximately 0.025 mm) of the substrate surface. By
comparison, an earlier approach such as that described in the U.S.
Pat. No. 6,821,563 to Yudovsky, cited earlier, required gas flow
around the edges of channel sidewalls and was thus limited to 0.5
mm or greater distance to the substrate surface. Positioning the
deposition device 10 closer to the substrate surface is preferred
in the present invention. In a preferred embodiment, distance D
from the surface of the substrate can be 0.4 mm or less, preferably
within 0.3 mm, more preferably within 0.25 mm of the output face of
the deposition device or the bottom of the guide walls that provide
the flow channels.
[0096] The cross-sectional views of FIGS. 8A and 8B show why it is
desirable to have the distance D relatively small, consistent with
the operation of the invention. In these figures, deposition device
10 is moving over substrate 20 from left to right, as the arrow
indicates. As output channel 12 carrying a reactive gaseous
material M moves to the right over an area, it encounters a
diffusion layer 72 from the next adjacent (previous-in-time) output
channel that is primarily inert gaseous material I. In order to
react on the surface of substrate 20, reactive gaseous material M
must diffuse through diffusion layer 72, which has a thickness
proportional to distance D. By comparison, FIG. 8B shows what
happens when distance D is reduced: diffusion layer 72 is reduced
proportionately. Diffusion through diffusion layer 72 happens more
quickly and more efficiently, allowing less waste and reducing the
overall amount of time needed for reaction on the surface of
substrate 20. The lower partition walls 22 also prevent less gas to
remain from the previous-in time output channel gas. It should be
noted that the flow of the gases in the channels are perpendicular
to the page of the FIGS. 8A and 8B, as shown by the back of the
arrow, which flow maintains a concentration gradient that aids the
diffusion through the thin diffusion layer 72 to the surface of the
substrate 20. The surface is exposed to the gas flow of M for
sufficient time for diffusion and any mixing to replace the
previous-in-time output channel gas. In this particular embodiment,
the flow of gas is across the surface rather than directly into the
surface so that it limits the undesirable mixing of reactant gases
between outlet channels, which might otherwise be exacerbated by
relative oscillation of the manifold and/or substrate.
[0097] In order to provide smooth flow along the length of output
channel 12, gas output port 24 may be inclined at an angle away
from normal, as indicated in FIGS. 7A and 7B. Optionally, some type
of gas flow redirecting structure may also be employed to redirect
a downward flow from gas output port 24 so that it forms a gas flow
that runs substantially in parallel to output face 36.
[0098] The plan view of FIG. 9 shows output face 36 of a portion of
a deposition device 10 that can be used in one embodiment. For
optimizing directional gas flow in this particular embodiment,
redirecting plates 38 may be positioned in each of the output
channels 12 for directing reactant gaseous materials. In the
embodiment shown, only output channels 12 that deliver reactant
gaseous materials are provided with redirecting plates 38 and
exhaust ports 26. This particular arrangement may be advantageous
in some applications, where it is advantageous to surround
deposition device 10 with inert gas, such as to reduce unwanted
intake of ambient gases. However, redirecting plates 38 could be
used on all output channels 12. Also, exhaust ports 26 could be
used on some or all output channels 12. In another possible
embodiment, redirecting plates can be used on all channels, but the
outlet edge of the redirecting plate may be at a different x-axis
position depending upon which channel is considered. In particulars
it may be desirable to have the outlet edge position of the baffles
58 (as shown in FIGS. 7B and 7D) for the inert flows to be at lower
x-axis positions than those of the reactant gases so that the inert
purge flows can serve as mentioned above to isolate the various
channels.
[0099] FIG. 9 also shows the pattern of output channels in one
embodiment. Here, it has been found to be particularly advantageous
to provide inert gas channels I as the outermost channels of
deposition device 10. Oxidation channels with first reactant
gaseous material O are next to the outermost channels, since these
condition the surface for ALD reaction with the metallic component
of second reactant gaseous material M.
[0100] FIG. 10 shows one embodiment of a deposition device 10 that
can be used in the present process in which the channels of width
W, length L, and height H are formed from stacked metal plates 42
and 44 having apertures 40 forming ducts 46a,b,c. FIG. 11A shows an
exploded view of a single output channel 12 section of deposition
device 10 formed in this way, showing an arrangement of apertures
40 in alternating partition plates 42 and delivery plates 44. FIG.
11B shows a similar exploded view for an adjacent output channel
12. Ducts 46a, 46b, and 46c, formed by alignment of apertures 40,
extend through deposition device 10 and provide input conduits for
gaseous flow communication, accepting the different reactant and
inert gaseous materials from external sources and providing the
redirecting structures that provide gas flows along output face 36
described earlier. Baffles and other redirecting structures are not
shown in these figures, but could be provided using stacked plates
suitably structured, or applied after the device is assembled.
[0101] The exploded views of FIGS. 11A and 11B each show a single
output channel 12 formed from stacked plates 42 and 44. In the
example of FIG. 11A, output channel 12 provides gaseous material
provided from duct 46b. Ducts 46a and 46c conduct other gases past
this channel in the embodiment shown in FIG. 11A. Delivery plate
44, dimensioned and apertured differently than the partition plates
42 that bound output channel 12, contains a redirecting chamber 48
that redirects a portion of the gas in duct 46b into gas flow F1.
In the example of FIG. 11B, output channel 12 provides gaseous
material provided from duct 46a. Ducts 46b and 46c conduct other
gases past this channel in the embodiment shown in FIG. 11B. Plates
42 and 44 should be of a suitable metal for conducting the reactive
gaseous materials, such as stainless steel or other metal for
example.
[0102] It is desirable that when a large number of plates are
assembled for such an embodiment, the gas flow delivered to the
substrate is uniform across all of the channels delivering a
particle flow (I, M, or O). This can be accomplished by proper
design of the plates, such as having restrictions in some part of
the flow pattern for each plate which are accurately machined to
provide a reproducible pressure drop for each channel.
[0103] Although the method of stacking plates is a particularly
useful way of constructing a deposition device for use in this
invention, there are a number of other methods to build such
structures and may be useful in alternate embodiments of deposition
devices that can be used in the present process. For example, the
deposition device for use in the present process may be constructed
by direct machining of a metal block, or of several metal blocks
adhered together. Furthermore, molding techniques involving
internal mold features can be employed, as will be understood by
the skilled artisan. A deposition device can also be constructed
using any of a number stereolithography techniques.
[0104] As can be seen from the example embodiment of FIGS. 10, 11A,
and 11B, deposition device 10 can be constructed of very small
size, with each output channel 12 having the width of a sheet of
metal plating. For example, in one embodiment using the arrangement
of FIGS. 10, 11A, and 11B, output channel 12 is about 0.034 inches
(0.86 mm) in width W. Output channels 12 for different materials
could be fabricated at different thicknesses to obtain width W
ranges, preferably from about 0.01 inches (0.25 mm) to about 0.1
inches (2.5 mm) for a compact arrangement. The length L of output
channel 12 can vary, depending on the needed uniformity and desired
gas pressure. In one embodiment, output channel length L is about 3
inches (75 mm). The height H of output channels 12 formed from
extending portions of stacked plates 42 is about 0.1 inches in one
embodiment.
[0105] Because gas flow can inadvertently draw ambient gases, due
to low-pressure zones that are created, it may be useful to provide
additional protection barrier from an inert layer. Referring to
FIG. 12, there is shown an envelopment gas flow F.sub.E by which an
additional flow of inert gas is used on one or more sides of
deposition device 10 to prevent ambient gases from contaminating
the process gases.
[0106] As was particularly described with reference to FIGS. 4A and
4B, deposition device 10 requires movement relative to the surface
of substrate 20 in order to perform its deposition function. This
relative movement can be obtained in a number of ways, including
movement of either or both deposition device 10 and substrate 20,
such as by movement of a process that provides a substrate support.
Movement can be oscillating or reciprocating or could be continuous
movement, depending on how many deposition cycles are needed.
Rotation of a substrate can also be used, particularly in a batch
process, although continuous processes are preferred.
[0107] Typically, ALD requires multiple deposition cycles, building
up a controlled film depth with each cycle. Using the nomenclature
for types of gaseous materials given earlier, a single cycle can,
for example in a simple design, provide one application of first
reactant gaseous material O and one application of second reactant
gaseous material M.
[0108] The distance between output channels for O and M reactant
gaseous materials determines the needed distance for reciprocating
movement to complete each cycle. For the example deposition device
10 of FIG. 9, having a nominal channel width of 0.034 inches in
width W for each output channel 12, reciprocating motion (along the
y axis as used herein) of at least 0.20 inches would be required.
For this example, an area of substrate 20 would be exposed to both
first reactant gaseous material O and second reactant gaseous
material M with movement over this distance. In some cases,
consideration for uniformity may require a measure of randomness to
the amount of reciprocating motion in each cycle, such as to reduce
edge effects or build-up along the extremes of reciprocation
travel.
[0109] A deposition device 10 may have only enough output channels
12 to provide a single cycle. Alternately, deposition device 10 may
have an arrangement of multiple cycles, enabling it to cover a
larger deposition area or enabling its reciprocating motion over a
distance that allows two or more deposition cycles in one traversal
of the reciprocating motion distance.
[0110] In one embodiment, a given area of the substrate is exposed
to a gas flow in a channel for less than 500 milliseconds,
preferably less than 100 milliseconds. The relative movement of the
substrate to a channel during oscillation is at a speed of at least
0.1 cm/sec, and the gas flow in the channels is at least 1
cm/sec.
[0111] Preferably, the temperature of the substrate during
deposition is under 300.degree. C., more preferably under
250.degree. C.
[0112] For example, in one particular application, it was found
that each O-M cycle formed a layer of one atomic diameter over
about 1/4 of the treated surface. Thus, four cycles, in this case,
are needed to form a uniform layer of 1 atomic diameter over the
treated surface. Similarly, to form a uniform layer of 10 atomic
diameters in this case, then, 40 cycles would be required.
[0113] An advantage of the reciprocating motion used for a
deposition device 10 used in one embodiment of the present process
is that it allows deposition onto a substrate 20 whose area exceeds
the area of output face 36. FIG. 13 shows schematically how this
broader area coverage can be effected, using reciprocating motion
along the y axis as shown by arrow R and also movement orthogonal
or transverse to the reciprocating motion, relative to the x axis.
Again, it must be emphasized that motion in either the x or y
direction, as shown in FIG. 13, can be effected either by movement
of deposition device 10, or by movement of substrate 20 provided
with a substrate support 74 that provides movement, or by movement
of both deposition device 10 and substrate 20.
[0114] In FIG. 13 the relative motion of the depositor and the
substrate are perpendicular to each other. It is also possible to
have this relative motion in parallel. In this case, the relative
motion needs to have a nonzero frequency component that represents
the oscillation and a zero frequency component that represents the
displacement of the substrate. This combination can be achieved by:
an oscillation combined with displacement of the deposition device
over a fixed substrate; an oscillation combined with displacement
of the substrate relative to a fixed substrate deposition device;
or any combinations wherein the oscillation and fixed motion are
provided by movements of both substrates.
[0115] In a preferred embodiment, ALD can be performed at or near
atmospheric pressure and over a broad range of ambient and
substrate temperatures, preferably at a temperature of under
300.degree. C. Preferably, a relatively clean environment is needed
to minimize the likelihood of contamination; however, full "clean
room" conditions or an inert gas-filled enclosure would not be
required for obtaining good performance when using preferred
embodiments of the process of the present invention.
[0116] FIG. 14 shows one embodiment of an Atomic Layer Deposition
(ALD) 60 process for making a metal-oxide-based encapsulation
layer, having a chamber 50 for providing a relatively
well-controlled and contaminant-free environment. Gas supplies 28a,
28b, and 28c provide the first, second, and third gaseous materials
to deposition device 10 through supply lines 32. The optional use
of flexible supply lines 32 facilitates ease of movement of
deposition device 10. For simplicity, an optional vacuum vapor
recovery process and other support components are not shown in FIG.
14 but could also be used. A transport subsystem 54 provides a
substrate support that conveys substrate 20 along output face 36 of
deposition device 10, providing movement in the x direction, using
the coordinate axis system employed in the present disclosure.
Motion control, as well as overall control of valves and other
supporting components, can be provided by a control logic processor
56, such as a computer or dedicated microprocessor assembly, for
example. In the arrangement of FIG. 14, control logic processor 56
controls an actuator 30 for providing reciprocating motion to
deposition device 10 and also controls a transport motor 52 of
transport subsystem 54.
[0117] FIG. 15 shows an alternate embodiment of an Atomic Layer
Deposition (ALD) process 70 for thin film deposition of
metal-oxide-based encapsulation layer onto a web substrate 66 that
is conveyed past deposition device 10 along a web conveyor 62 that
acts as a substrate support. A deposition device transport 64
conveys deposition device 10 across the surface of web substrate 66
in a direction transverse to the web travel direction. In one
embodiment, deposition device transport 64 uses a lead screw that
traverses the width of web substrate 66. In another embodiment,
multiple deposition devices 10 are used, at suitable positions
along web 62.
[0118] FIG. 16 shows another Atomic Layer Deposition (ALD) system
70 for depositing a metal-oxide-based encapsulating layer in a web
arrangement, using a stationary deposition device 10 in which the
flow patterns are oriented orthogonally to the configuration of
FIG. 14. In this arrangement, motion of web conveyor 62 itself
provides the movement needed for ALD deposition. Reciprocating
motion could also be used in this environment, such as by
repeatedly reversing the direction of rotation of a web roller to
move substrate 66 forward and backwards relative to deposition
device 10. Reciprocation motion can also be obtained by allowing a
reciprocating motion of the deposition device across an arc whose
axis coincides with the roller axis, while the web is moved in a
constant motion. Referring to FIG. 17, an embodiment of a portion
of deposition device 10 is shown in which output face 36 has an
amount of curvature, which might be advantageous for some web
coating applications. Convex or concave curvature could be
provided. It will be understood that in other embodiments, nitrides
or other materials can be used rather than oxides, as long as they
produce an inorganic material that is a dielectric having the
desired barrier properties for moisture and air.
[0119] Optionally, the present process can be accomplished with
other apparatus or systems described in more detail in commonly
assigned U.S. application Ser. No. 11/392,007, U.S. application
Ser. No. 11/392,006, U.S. application Ser. No. 11/620,744, and U.S.
application Ser. No. 11/620,740. All the above-identified
applications incorporated by reference in their entirety.
[0120] In the embodiments in the latter three applications, a
delivery device having an output face for providing gaseous
materials for thin-film material deposition onto a substrate
comprises elongated emissive channels in at least one group of
elongated emissive channels, of the three groups of elongated
emissive channels (namely, at least one group of: (i) one or more
first elongated emissive channels, (ii) one or more second
elongated channels, and (iii) a plurality of third elongated
channels) that is capable of directing a flow, respectively, of at
least one of the first gaseous material, second gaseous material,
and the third gaseous material substantially orthogonally with
respect to the output face of the delivery device, which flow of
gaseous material is capable of being provided, either directly or
indirectly from each of the elongated emissive channels in the at
least one group, substantially orthogonally to the surface of the
substrate.
[0121] Each elongated channel is associated with an elongated
output opening, substantially parallel to other elongated output
openings, in the face of the delivery device, which opening can be
connected to the elongated channel or can directly be the outlet
opening of the channel.
[0122] In one embodiment, apertured plates are disposed
substantially in parallel to the output face, and apertures on at
least one of the apertured plates form the first, second, and third
elongated emissive channels. In an alternative embodiment, the
apertured plates are substantially perpendicularly disposed with
respect to the output face.
[0123] In one such embodiment, the deposition device comprises
exhaust channels, for example, a delivery device for thin-film
material deposition onto a substrate comprising: (a) a plurality of
inlet ports comprising at least a first inlet port, a second inlet
port, and a third inlet port capable of receiving a common supply
for a first reactive gaseous material, a second reactive gaseous
material, and a third (inert purge) gaseous material, respectively;
(b) at least one exhaust port capable of receiving exhaust gas from
thin-film material deposition and at least two elongated exhaust
channels, each of the elongated exhaust channels capable of gaseous
fluid communication with the at least one exhaust port; and (c) at
least three pluralities of elongated output channels, (i) a first
plurality of first elongated output channels, (ii) a second
plurality of second elongated output channels, and (iii) a third
plurality of third elongated output channels, each of the first,
second, and third elongated output channels capable of gaseous
fluid communication, respectively, with one of the corresponding
first inlet port, second inlet port, and third inlet port; wherein
each of the first, second, and third elongated output channels and
each of the elongated exhaust channels extend in a length direction
substantially in parallel; wherein each first elongated output
channel is separated on at least one elongated side thereof from a
nearest second elongated output channel by a relatively nearer
elongated exhaust channel and a relatively less near third
elongated output channel; and wherein each first elongated output
or emissive channel and each second elongated output or emissive
channel is situated between relatively nearer elongated exhaust
channels and between relatively less nearer elongated output or
emissive channels.
[0124] Further embodiments can comprise a gas diffuser associated
with at least one group of the three groups of elongated emissive
channels such that at least one of the first, second, and third
gaseous material, respectively, is capable of passing through the
gas diffuser prior to delivery from the delivery device to the
substrate, during thin-film material deposition onto the substrate,
and wherein the gas diffuser maintains flow isolation of the at
least one of first, second, and third gaseous material downstream
from each of the elongated emissive channels in the at least one
group of elongated emissive channels.
[0125] In one embodiment such a gas diffuser is capable of
providing a friction factor for gaseous material passing there
through that is greater than 1.times.10.sup.2, thereby providing
back pressure and promoting equalization of pressure where the flow
of the at least one first, second and third gaseous material exits
the delivery device. In one embodiment of the invention, the gas
diffuser comprises a porous material through which the at least one
of the first, second, and third gaseous material passes. In a
second embodiment of the invention, the gas diffuser comprises a
mechanically formed assembly comprising at least two elements
comprising interconnected passages, for example, in which nozzles
are connected to a flow path provided by a thin space between
parallel surface areas in the two elements.
[0126] In one embodiment, the one or more of the gas flows from the
deposition devices provides a pressure that at least contributes to
the separation of the surface of the substrate from the face of the
delivery head, thereby providing a "floating head" or "air bearing"
type deposition head, which can help to stabilize the gas flows and
limit intermixing of the gas flows.
[0127] The process of the present invention is advantaged in its
capability to perform deposition onto a substrate over a broad
range of temperatures, including room or near-room temperature in
some embodiments. The process of the present invention can operate
in a vacuum environment, but is particularly well suited for
operation at or near atmospheric pressure.
[0128] Devices that may be encapsulated by this method are not
constrained by their substrate, or support; devices may include
supports that are organic or inorganic materials. For example, the
support may comprise inorganic glasses, ceramic foils, polymeric
materials, filled polymeric materials, coated metallic foils,
acrylics, epoxies, polyamides, polycarbonates, polyimides,
polyketones,
poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene)
(sometimes referred to as poly(ether ether ketone) or PEEK),
polynorbornenes, polyphenyleneoxides, poly(ethylene
naphthalenedicarboxylate) (PEN), poly(ethylene terephthalate)
(PET), poly(ether sulfone) (PES), poly(phenylene sulfide) (PPS),
and fiber-reinforced plastics (FRP). Flexible substrates can also
be thin metal foils such as stainless steel provided they are
coated with an insulating layer for electrical isolation as
necessary for the OLED device. A flexible support, in some
embodiments of the present invention, allows for roll processing,
which may be continuous, providing economy of scale and economy of
manufacturing over flat and/or rigid supports. The flexible support
chosen preferably is capable of wrapping around the circumference
of a cylinder of less than about 50 cm diameter, more preferably 25
cm diameter, most preferably 10 cm diameter, without distorting or
breaking, using low force as by unaided hands. The preferred
flexible support may be rolled upon itself. However, if flexibility
is not a concern, then the substrate may be a wafer or sheet made
of materials including glass and silicon. The thickness of the
substrate may vary, and according to particular examples it can
range from about 100 .mu.m to about 1 cm.
[0129] Referring to FIG. 20, an OLED device 108 according to one
embodiment of the present invention comprises a substrate 110, a
first electrode 112, a conductive electrode 116, an encapsulating
package 117 having a thickness between 10 nm and 10,000 nm,
preferably less than 500 nm, more preferably 100 to 250 nm, one or
more organic layers 114 formed between the first electrode 112 and
the conductive electrode 116, at least one organic layer 114 being
a light-emitting layer; and a patterned auxiliary electrode 126 in
electrical contact with the conductive electrode 116.
[0130] In a top-emitter embodiment of an OLED device, the thin film
encapsulating package 117 is formed over a transparent top
conductive electrode 116 and the first electrode 112 is a bottom
electrode. The bottom electrode may be reflective. It is preferred
that the conductive electrode 116 has a refractive optical index
equal to or greater than the refractive optical index of the one or
more organic layers 114. By providing such relative refractive
indices, light emitted from the organic layers 114 will not be
trapped by total internal reflection in the organic layers 114
since light may travel from the organic layers 114 into the equal-
or higher-index conductive electrode 116.
[0131] Thin-film electronic components 130 having planarization
layers 132 may be employed to control the OLED device, as is known
in the art. A cover 120 is provided over the OLED and electrode
layers and adhered to the substrate 110 to protect the OLED device,
for example using an adhesive 160.
[0132] The bottom first electrode 112 can be patterned to form
light-emitting areas 150, 152, and 154 while a patterned auxiliary
electrode 126 may be formed between the light-emitting areas (as
shown) or under the light-emitting areas (not shown). The
conductive electrode 116 may be unpatterned and formed continuously
over the organic layers 114.
[0133] In some embodiments of the present invention (FIG. 2), the
light-emitting organic layer 114 may emit white light, in which
case color filters 140R, 140G, 140B may be formed, for example on
the cover 120, to filter light to provide a full-color
light-emissive device with colored light-emitting areas 150, 152,
and 154.
[0134] In various embodiments of the present invention, the
auxiliary electrode 126 may be formed on the side of the conductive
electrode 116 opposite the one or more organic layers 114, as shown
in FIG. 21. Such layers may be deposited by sputtering or
evaporating metals through masks, for example as described in U.S.
Pat. No. 6,812,637 entitled "OLED DISPLAY WITH AUXILIARY ELECTRODE"
by Cok et al. As shown in FIG. 21, the auxiliary electrode 126 may
be formed on the side of the one or more organic layers 114
opposite the conductive electrode 116 and may be electrically
connected to the conductive electrode 116 through vias 134 formed
in the one or more organic layers 114. The auxiliary electrode 126
may be formed using conventional photolithographic techniques while
the vias 134 may be formed using laser ablation, for example, as
described in U.S. Pat. No. 6,995,035 entitled "METHOD OF MAKING A
TOP-EMITTING OLED DEVICE HAVING IMPROVED POWER DISTRIBUTION" by Cok
et al. Materials employed in forming the auxiliary electrode may
include, e.g., aluminum, silver, magnesium, and alloys thereof.
[0135] As employed herein, an encapsulating package 117 comprises
one or more layers, preferably 2 to 15, depending on the thickness
of each layer. Such layers are applied to the OLED device by atomic
layer deposition as described above and in the Examples, thereby
providing an encapsulating package 117 resistive to penetration by
moisture and oxygen. Generally, it is preferred to form the
encapsulating package 117 at a temperature less than 140 degrees C.
to avoid damaging organic layers. Alternatively, the encapsulating
package 117 may be formed at a temperature less than 120 degrees C.
or less than 110 degrees C.
[0136] Each encapsulating layer is formed by alternately providing
a first reactive gaseous material and a second reactive gaseous
material, wherein the first reactive gaseous material is capable of
reacting with the coated substrate treated with the second reactive
gaseous material. The first reactive gaseous material completely
covers the exposed surface of the OLED device, while the second
reactive gaseous material reacts with the first reactive gaseous
material to form a layer highly resistant to environmental
contaminants. Applicants have demonstrated the problems of the
conventional deposition art for encapsulating layers in protective
organic materials and the improvements found by employing an
encapsulating package according to the present invention.
[0137] A wide variety of metal oxides, nitrides, and other
compounds may be employed to form the thin film encapsulation
package. The thin film encapsulation package, for example, can
comprise zinc oxide in combination with at least one other
compound, in separate layers or the same layer. The other compound
can be a complex mixture created by applying dopants, for example
by employing indium with tin oxide to form indium tin oxide.
Suitably, an encapsulating material can be made using an inorganic
compound that is a dielectric oxide selected from the group
consisting of Al.sub.2O.sub.3, SiO.sub.2, TiO.sub.2, ZrO.sub.2,
MgO, HfO.sub.2, Ta.sub.2O.sub.5, aluminum titanium oxide, tantalum
hafnium oxide, and indium tin oxide.
[0138] A variety of thicknesses may be employed for the thin film
encapsulation package, depending on the subsequent processing of
the device and environmental exposure. The thickness of the thin
film encapsulation package may be selected by controlling the
number of sequentially deposited layers of reactive gases.
[0139] A planarizing underlayer of parylene polymer can be used to
improve the performance of a thin film encapsulation package, as
will be appreciated by the skilled artisan. Parylene layers for
OLED encapsulation are disclosed in US 2006/0246811 by Winters et
al., hereby incorporated by reference. For example, a 120 nm
parylene or other suitable polymeric layer can be employed to
achieve the planarizing effect and presumably to serve as a buffer
layer for mitigating or augmenting stress force created by the
inorganic encapsulant layers.
[0140] Referring again to the OLED device of FIG. 20, substrate 110
may be opaque to the light emitted by OLED device 108. Common
materials for substrate 110 are glass or plastic. First electrode
112 may be reflective. Common materials for first electrode 112 are
aluminum and silver or alloys of aluminum and silver. Organic
Electroluminescent (EL) element 114 includes at least a light
emitting layer (LEL) but frequently also includes other functional
layers such as an electron transport layer (ETL), a hole transport
layer (HTL), an electron blocking layer (EBL), or a hole blocking
layer (HBL), and other suitable functional layers known in the art.
The discussion that follows is independent of the number of
functioning layers and independent of the materials selection for
the organic EL element 114. Often a hole injection layer is added
between organic EL element 114 and the anode and often an electron
injection layer is added between organic EL element 114 and the
cathode. In operation, a positive electrical potential is applied
to the anode and a negative potential is applied to the cathode.
Electrons are injected from the cathode into organic EL element 114
and driven by the applied electrical field to move toward the
anode; holes are injected from the anode into organic EL element
114 and driven by the applied electrical field to move toward the
cathode. When electrons and holes combine in organic EL element
114, light is generated and emitted by OLED device 108.
[0141] Material for the conductive electrode 116 can include
inorganic oxides such as indium oxide, gallium oxide, zinc oxide,
tin oxide, molybdenum oxide, vanadium oxide, antimony oxide,
bismuth oxide, rhenium oxide, tantalum oxide, tungsten oxide,
niobium oxide, or nickel oxide. These oxides are electrically
conductive because of non-stoichiometry. The resistivity of these
materials depends on the degree of non-stoichiometry and mobility.
These properties as well as optical transparency can be controlled
by changing deposition conditions.
[0142] The range of achievable resistivity and optical transparency
can be further extended by impurity doping. An even larger range of
properties can be obtained by mixing two or more of these oxides.
For example, mixtures of indium oxide and tin oxide, indium oxide
and zinc oxide, zinc oxide and tin oxide, or cadmium oxide and tin
oxide have been the most commonly used transparent conductors.
[0143] A top-emitting OLED device may be formed by providing a
substrate 110 with a bottom first electrode 112 and one or more
organic layers 114 formed thereon, at least one organic layer being
a light-emitting layer, forming a conductive protective top
electrode 16 comprising a transparent conductive oxide over the one
or more organic layers opposite the bottom electrode 112 wherein
the conductive electrode 116 is a layer having a thickness less
than 100 nm, and forming a patterned auxiliary electrode 126 in
electrical contact with the conductive electrode 116.
[0144] Alternatively, a bottom-emitting OLED device may be formed
by providing a conductive protective bottom electrode comprising a
transparent conductive oxide layer, as will be appreciated by the
skilled artisan.
[0145] OLED devices of this invention can also employ various
well-known optical effects in order to enhance their properties if
desired. This includes optimizing the encapsulation package to
yield maximum light transmission. providing anti-glare or
anti-reflection coatings over the display, providing a polarizing
medium over the display, or providing colored, neutral density, or
color conversion filters over the display. Separate layers of
filters, polarizers, and anti-glare or anti-reflection coatings may
be specifically provided over the encapsulation package or included
as a pre-designed characteristic of the encapsulation package,
especially in the case of a multilayer encapsulation package. Such
optical films are further described in U.S. patent application Ser.
No. ______ (docket 93465) to Fedorovskaya et al., concurrently
filed, hereby incorporated by reference in its entirety.
[0146] The present invention may also be practiced with either
active- or passive-matrix OLED devices. It may also be employed in
display devices or in area illumination devices. In a preferred
embodiment, the present invention is employed in a flat-panel OLED
device composed of small-molecule or polymeric OLEDs as disclosed
in but not limited to U.S. Pat. No. 4,769,292, issued Sep. 6, 1988
to Tang et al., and U.S. Pat. No. 5,061,569, issued Oct. 29, 1991
to VanSlyke et al. Many combinations and variations of organic
light-emitting displays can be used to fabricate such a device,
including both active- and passive-matrix OLED displays having
either a top- or bottom-emitter architecture.
EXAMPLES
Description of the Coating Apparatus
[0147] All of the following thin film examples employ a coating
apparatus, for atomic layer deposition, having the flow setup
indicated in FIG. 3, which is a block diagram of the source
materials for a thin film deposition process according to the
Examples.
[0148] The flow setup is supplied with nitrogen gas flow 81 that
has been purified to remove oxygen and water contamination to below
1 ppm. The gas is diverted by a manifold to several flow meters
which control flows of purge gases and of gases diverted through
bubblers to select the reactive precursors. In addition to the
nitrogen supply, air flow 90 is also delivered to the apparatus.
The air is pretreated to remove moisture.
[0149] The following flows are delivered to the ALD coating
apparatus: metal (zinc) precursor flow 92 containing metal
precursors diluted in nitrogen gas; oxidizer-containing flow 93
containing non-metal precursors or oxidizers diluted in nitrogen
gas; and nitrogen purge flow 95 composed only of the inert gas. The
composition and flows of these streams are controlled as described
below.
[0150] Gas bubbler 82 contains diethylzinc. Gas bubbler 83 contains
trimethylaluminum. Both bubblers are kept at room temperature. Flow
meters 85 and 86 deliver flows of pure nitrogen to the diethylzinc
bubbler 82 and trimethylaluminum bubbler 83, respectively. The
flows of trimethylaluminum and diethylzinc can be alternately or
sequentially supplied to the OLED device in order to provide
alternating encapsulating layers on the OLED device or they can be
supplied simultaneously for a mixed layer.
[0151] The output of the bubblers contain nitrogen gas saturated
with the respective precursor solutions. These output flows are
mixed with a nitrogen gas dilution flow delivered from flow meter
87 to yield the overall flow of metal precursor flow 92. In the
following examples, the flows will be as follows: [0152] Flow meter
85: To Diethylzinc Bubbler Flow [0153] Flow meter 86: To
Trimethylaluminum Bubbler Flow [0154] Flow meter 87: To Metal
Precursor Dilution Flow
[0155] Gas bubbler 84 contains pure water for the control (or
ammonia in water for the inventive example) at room temperature.
Flow meter 88 delivers a flow of pure nitrogen gas to gas bubbler
84, the output of which represents a stream of saturated water
vapor. An airflow is controlled by flow meter 91. The water bubbler
output and air streams are mixed with dilution stream from flow
meter 89 to produce the overall flow of oxidizer-containing flow 93
which has a variable water composition, ammonia composition, oxygen
composition, and total flow. In the following examples, the flows
will be as follows: [0156] Flow meter 88: To Water Bubbler [0157]
Flow meter 89: To Oxidizer Dilution Flow [0158] Flow meter 91: To
Air Flow
[0159] Flow meter 94 controls the flow of pure nitrogen that is to
be delivered to the coating apparatus.
[0160] Streams or Flows 92, 93, and 95 are then delivered to an
atmospheric pressure deposition device 10 where they are directed
out of the channels or microchamber slots as indicated in FIG. 4. A
gap 96 of approximately 0.15 mm exists between the elongated
channels (not shown) and the substrate 97. The microchambers are
approximately 2.5 mm tall, 0.86 mm wide, and run the length of the
deposition device 10 which is 76 mm. The reactant materials in this
configuration are delivered to the middle of the slot and flow out
of the front and back.
[0161] In order to perform a deposition, the deposition device 10
is positioned over a portion of the substrate 97 and then moved in
a reciprocating fashion over the substrate, as represented by the
arrow 98. The length of the reciprocation cycle was 32 mm. The rate
of motion of the reciprocation cycle is 30 mm/sec.
[0162] The following characterization is used:
Description of OLED Test Conditions, Measurement and Analysis
[0163] The test conditions used to evaluate the OLED devices
included:
[0164] (1) lighting them up by applying voltage to the cathode and
anode,
[0165] (2) photographing lit up devices with a Sony XC-75 black and
white CCD camera with 3.72 .mu.m/pixel resolution and 40.times.
magnification. For accurate dark spot evaluation the voltage was
applied to the device to produce the best visual contrast for
recognizing existence and measurements of the dark spots on the
test icon,
[0166] (3) storing OLED devices either at room temperature of
24.degree. C. and 50% relative humidity (RH) for a certain period
of time (some devices), or
[0167] (4) storing the devices in a humidity chamber (HC) at
85.degree. C./85% (85/85) RH (relative humidity) in an accelerated
humidity/oxygen resistance test.
Materials Used:
[0168] (1) Me.sub.3Al (commercially available from Aldrich Chemical
Co.)
[0169] (2) Et.sub.2Zn (commercially available from Aldrich Chemical
Co.)
Description of the Encapsulation Process Using the Coating
Apparatus
[0170] An OLED device was constructed as detailed below for various
inventive and comparative OLED devices. After forming the cathode
layer, the OLED device was taken from the clean room and exposed to
the atmosphere prior to depositing the thin film encapsulating
layer. The 2.5.times.2.5 inch square (62.5 mm square) OLED device
was positioned on a platen, held in place by a vacuum assist, and
heated to 110.degree. C. The platen with the glass substrate was
positioned under the deposition device 10 of the deposition
apparatus that directs the flow of the active precursor gasses. The
spacing between the device and the coating head was adjusted using
a micrometer to 30 microns.
[0171] The deposition device 10 has isolated channels through which
flow: (1) inert nitrogen gas; (2) a mixture of nitrogen, air and
water vapor; and (3) a mixture of active metal alkyl vapor
(Me.sub.3Al or Et.sub.2Zn) in nitrogen. The flow rate of the active
metal alkyl vapor was controlled by bubbling nitrogen through the
pure liquid (Me.sub.3Al or Et.sub.2Zn) contained in an airtight
bubbler by means of individual mass flow control meters. The flow
of water vapor was controlled by adjusting the bubbling rate of
nitrogen passed through pure water in a bubbler. The temperature of
the coating head was maintained at 40.degree. C. The coating
process was initiated by oscillating the coating head across the
substrate for the number of cycles specified.
[0172] In the following experiments, a flow rate of 26 sccm or 13
sccm was used to supply the diethylzinc. A flow rate of 4 sccm was
used to supply the trimethylaluminum bubbler flow. A flow rate of
180 sccm or 150 sccm was used to supply the metal precursor
dilution flow. A flow rate of 15 sccm was used to supply the water
bubbler. A flow rate of 180 sccm or 150 sccm was used to supply the
oxidizer dilution flow. A flow rate of 37.5 sccm or 31.3 sccm was
used to supply the air flow.
[0173] The deposition process was calibrated to determine the
number of cycles to produce the desired thickness of zinc oxide or
aluminum oxide layers. This number of cycles was then used to coat
an OLED device with the encapsulation layer or layers, as desired.
Immediately after encapsulation, the device was lit by applying
voltage to the electrodes.
Comparative Examples 1-2
[0174] A Comparative Device 1 and Comparative Device 2 were
constructed in the following manner.
[0175] 1. A glass substrate coated with about a 21.5 nm layer of
indium-tin oxide (ITO), as the anode, was sequentially
ultrasonicated in a commercial detergent, rinsed in deionized
water, degreased in toluene vapor and exposed to an oxygen plasma
for about 1 min.
[0176] 2. Over the ITO was deposited a thin layer of a
hole-injecting material (HIL). For Comparative Device 1,
fluorocarbon (CF.sub.x) was applied by plasma-assisted deposition
of CHF.sub.3, as described in U.S. Pat. No. 6,208,075 by Hung et
al. Comparative Device 2 used a different HIL material.
[0177] 3. Subsequently a layer (HTL) of hole-transporting material
4,4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was deposited
to a thickness of 75 nm.
[0178] 4. Next, an electron-transporting layer (ETL) and
light-emitting layer (LEL) corresponding to 75 nm of
tris(8-quinolinolato)aluminum (III) (Alq) were
vacuum-deposited.
[0179] 5. A 0.5 nm electron-injecting layer of lithium fluoride was
vacuum deposited onto the ETL, followed by a 150 nm layer of
aluminum to form a cathode layer.
[0180] The above sequence completed the deposition of the OLED
devices. The Comparative Devices 1 and 2 were left unencapsulated
as comparisons.
[0181] The OLED devices without an encapsulation layer when lit
showed a large number of dark spots. After storage in the humidity
chamber, the devices could not be lit. Organic layers hydrolyzed,
and the aluminum cathode layer oxidized and became transparent. The
OLED devices without encapsulation showed rapid growth of dark
spots. After 7 days, when stored in an ambient environment, the
devices could not be lit.
Inventive Example 1
[0182] Various multilayers of a Al.sub.2O.sub.3/ZnO stack, wherein
the number and thickness of the layers were varied were made and
tested. The multilayer stacks were about 2000 .ANG. in total
thickness. The coating for these two inventive devices comprised
the following combination of layers:
TABLE-US-00001 Al.sub.2O.sub.3 120 .ANG. ZnO 100 .ANG.
Al.sub.2O.sub.3 100 .ANG. ZnO 150 .ANG. Al.sub.2O.sub.3 200 .ANG.
ZnO 200 .ANG. Al.sub.2O.sub.3 1000 .ANG.
[0183] The results showed that the multilayered film stacks
consisting of Al.sub.2O.sub.3 and ZnO layers exhibited less or no
cracks, meaning that the stress was better accommodated by the
multilayer film stacks.
[0184] It was also shown that the multilayered Al.sub.2O.sub.3/ZnO
film stacks can provide good protection: two of the inventive
devices exhibited no dark spot growth in the center of the OLED
pixels (edge growth can be eliminated by optimization of the
geometry and the flow rates) after 24 and 48 hours in a humidity
chamber.
Inventive Example 2
[0185] An OLED device was coated with an encapsulation film
containing a mixture of Al.sub.2O.sub.3/ZnO prepared by combining
precursors for two oxides in the microchamber slots of a spatially
dependent atomic layer deposition head, using water in another
channel.
[0186] A total of 450 oscillation cycles of the delivery head was
performed. During the coating process, a 120 .ANG. layer of pure
Al.sub.2O.sub.3 was first deposited. Then the flows of metal
precursors to the trimethylaluminum bubbler flow and to the
diethylzinc bubbler flow were gradually modified to increase the
relative amount of ZnO and decrease the relative amount of
Al.sub.2O.sub.3 until the film reached 100% of ZnO. Then the
process was repeated in the opposite direction, diminishing the
relative amount of ZnO while increasing the relative amount of
Al.sub.2O.sub.3 such that the final 100 .ANG. of material consisted
of Al.sub.2O.sub.3 only. The total thickness of the mixed
Al.sub.2O.sub.3/ZnO film was approximately 2000 .ANG..
[0187] After the coating process was completed, the voltage was
applied to the electrodes and the dark spots were characterized.
The device was then kept at 25 degrees C and 50% RH for 7 days.
During this period the device was repeatedly tested and
demonstrated no or minimal growth of dark spots when lit. In
comparison to the unencapsulated device kept in similar conditions,
the mixed film of Al.sub.2O.sub.3 and ZnO provided significantly
better protection against moisture and air.
[0188] The results showed that the film can be deposited crack-free
or with lesser cracks. The mixed Al.sub.2O.sub.3/ZnO did not
perform in the humidity chamber as well as the multilayer film
stacks, supposedly because of the difficulty to control the
composition in the current deposition system and elements of gas
mixing, but the mixed Al.sub.2O.sub.3/ZnO film was still superior
to the single Al.sub.2O.sub.3 or single ZnO film.
[0189] The invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
PARTS LIST
[0190] 1 continuous supply of gaseous materials for system [0191] 2
first channel flow of first molecular precursor over channel are of
substrate [0192] 3 relative movement of substrate and multi-channel
flows [0193] 4 second channel flow with inert gas over channel area
[0194] 5 relative movement of substrate and multi-channel flows
[0195] 6 third channel flow of second molecular precursor over
channel area [0196] 7 relative movement of substrate and
multi-channel flows [0197] 8 fourth channel flow with inert gas
over channel area [0198] 9 relative movement of substrate and
multi-channel flow [0199] 10 deposition device [0200] 11 multiple
channel flow in parallel [0201] 12 output channel [0202] 14, 16, 18
gas inlet port [0203] 15 sequence [0204] 20 substrate [0205] 22
partition [0206] 24 gas output port [0207] 26 exhaust port [0208]
28a, 28b, 28c gas supply [0209] 30 actuator [0210] 32 supply line
[0211] 36 output face [0212] 38 redirecting plate [0213] 40
aperture [0214] 42 partition plate [0215] 44 delivery plate [0216]
46a, 46b, 46c duct [0217] 48 redirecting chamber [0218] 50 chamber
[0219] 52 transport motor [0220] 54 transport subsystem [0221] 56
control logic processor [0222] 58 baffle [0223] 60 Atomic Layer
Deposition (ALD) process [0224] 62 web conveyor [0225] 64
deposition device transport [0226] 66 web substrate [0227] 70
Atomic Layer Deposition (ALD) process [0228] 72 diffusion layer
[0229] 74 substrate support [0230] 81 nitrogen gas flow [0231] 82,
83, 84 gas bubbler [0232] 85, 86, 87, 88 flow meter [0233] 89, 91,
94 flow meter [0234] 90 air flow [0235] 92 metal precursor flow
[0236] 93 oxidizer-containing flow [0237] 95 nitrogen purge flow
[0238] 96 gap [0239] 97 example substrate [0240] 98 arrow [0241]
108 OLED device [0242] 110 substrate [0243] 112 first electrode
[0244] 114 organic element layer [0245] 116 second, conductive
electrode [0246] 117 thin film encapsulating package [0247] 120
cover [0248] 126 auxiliary electrode [0249] 130 thin film
electronic components [0250] 132 planarization layers [0251] 134
via [0252] 140R color filter [0253] 140G color filter [0254] 140B
color filter [0255] 150 light-emitting area [0256] 152
light-emitting area [0257] 154 light-emitting area [0258] 160
adhesive [0259] D distance [0260] F1, F2, F3, F4 gas flow [0261]
F.sub.I, F.sub.O, F.sub.M, F.sub.E gas flow [0262] H height [0263]
I inert gaseous material [0264] L channel length [0265] M second
reactant gaseous material [0266] O first reactant gaseous material
[0267] R arrow [0268] W channel width
* * * * *