U.S. patent application number 11/266366 was filed with the patent office on 2006-04-06 for source for thermal physical vapor deposition of organic electroluminescent layers.
This patent application is currently assigned to LG Electronics Inc.. Invention is credited to Yoon Soo Han, Ki Beom Kim, Yoon Heung Tak.
Application Number | 20060070576 11/266366 |
Document ID | / |
Family ID | 36571445 |
Filed Date | 2006-04-06 |
United States Patent
Application |
20060070576 |
Kind Code |
A1 |
Kim; Ki Beom ; et
al. |
April 6, 2006 |
Source for thermal physical vapor deposition of organic
electroluminescent layers
Abstract
The present invention disclosed the deposition source installed
in a chamber, heated by applied electric power to transfer heat to
a vapor deposition material received therein and applying a
vaporized deposition material generated therein to a substrate to
form deposition organic electroluminescent layers onto the
substrate, and comprising a vessel consisted of a top plate on
which a vapor efflux aperture is formed, a side wall, and a bottom
wall; a heating means for supplying heat to the deposition material
received in the vessel, the heating means being capable of moving
vertically; and a means for moving the heating means (or the bottom
wall), the moving means (or the bottom wall) being operated in
response to the signal of a sensing means on varied distances
between the heating means and the surface of said deposition
material. Thus, the heating means is moved downward (or the bottom
wall) is moved upward by the moving means to maintain the distance
between the heating means (or the substrate to be coated) and the
surface of the deposition material at an initially-set value when
the thickness of the deposition material is decreased.
Inventors: |
Kim; Ki Beom; (Daeku,
KR) ; Han; Yoon Soo; (Kyongsangbuk-do, KR) ;
Tak; Yoon Heung; (Kumi-shi, KR) |
Correspondence
Address: |
FLESHNER & KIM, LLP
P.O. BOX 221200
CHANTILLY
VA
20153
US
|
Assignee: |
LG Electronics Inc.
|
Family ID: |
36571445 |
Appl. No.: |
11/266366 |
Filed: |
November 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10621471 |
Jul 18, 2003 |
|
|
|
11266366 |
Nov 4, 2005 |
|
|
|
Current U.S.
Class: |
118/727 ;
118/726 |
Current CPC
Class: |
C23C 14/12 20130101;
C23C 14/243 20130101; C23C 14/543 20130101; H01L 51/56
20130101 |
Class at
Publication: |
118/727 ;
118/726 |
International
Class: |
C23C 16/00 20060101
C23C016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2002 |
KR |
42271/2002 |
Sep 25, 2002 |
KR |
58116/2002 |
Oct 1, 2002 |
KR |
59786/2002 |
Claims
1-17. (canceled)
18. A deposition source installed in a chamber, to form deposition
organic electroluminescent layers onto a substrate, by applying a
vaporized deposition material generated therein to the substrate,
and by transferring heat to a vapor deposition material received
therein, heated by applied electric power, comprising; a top plate
on which a vapor efflux aperture is formed, a side wall, and a
bottom plate, said vapor efflux aperture having a length which is
longer than, or the same as, the width of said substrate to be
coated with a deposition organic electroluminescent layers.
19. The deposition source according to claim 18, wherein said
deposition source is capable of moving to the horizontal direction
with respect to said substrate.
20. The deposition source according to claim 18, wherein said
substrate is capable of moving to the horizontal direction with
respect to said deposition source.
21. The deposition source according to claim 18, wherein said
deposition source has the upper portion and the lower portion, said
upper portion has a sectional surface area smaller than that said
lower portion.
22. The deposition source according to claim 18, wherein said
deposition source is made from a material having thermal capacity
which is higher than said deposition material.
23. The deposition source according to claim 22, wherein said
deposition source is made of oxide or nitride of aluminum (Al),
zirconium (Zr), silicon (Si), or yttrium (Y), or composite material
of at least two above.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a deposition source for
thermal physical vapor deposition of organic electroluminescent
layers, and particularly to a deposition source capable of forming
a uniform electroluminescent layer on the entire surface of a
substrate by compensating increase of the distance between a
deposition material and a heating means (or the substrate) from
change of the thickness of the deposition material.
BACKGROUND OF THE INVENTION
[0002] Thermal physical vapor deposition process, which is one of
the processes for depositing an organic electroluminescent device,
is a technique to coat an electroluminescent layer on a substrate
in a housing with vaporized deposition material. In the deposition
process, the deposition material is heated to the point of
vaporization and the vapor of the deposition material is condensed
on the substrate to be coated after the deposition material is
moved out of the deposition source. This process is carried out
with both deposition source holding the material to be vaporized
and substrate to be coated in a vessel with the pressure range of
10.sup.-7 to 10.sup.-2 Torr.
[0003] Generally speaking, the deposition source to hold the
deposition material is made from electrically resistant materials
whose temperature is increased when electrical current is passed
through walls (member). When the electrical current is applied to
the deposition source, the deposition material inside is heated by
radiation heat from the walls and conduction heat from contact with
the walls. Typically, the deposition source is in the shape of box
with aperture to allow vapor efflux toward the direction of the
substrate.
[0004] Thermal physical vapor deposition source has been used to
vaporize and deposit onto the substrate layers comprised of a wide
range of materials, for example, organics of low temperature,
metals, or inorganic compounds of high temperature. In the case of
organic layer deposition, the starting material is generally
powder. Organic powder has been recognized as giving a number of
disadvantages for this type of thermal vaporization coating. First,
many organics are relatively complex compounds (high molecular
weight) with relatively weak bonding, and so intensive care must be
taken to avoid decomposition during the vaporization process.
Second, the powder form can give rise to particles of non-vaporized
electroluminescent materials. The particles leave the deposition
source with vapor and are deposited as undesirable lumps on the
substrate. Such lumps are also commonly referred to as particulate
or particulate inclusion in the layers formed on the substrate.
[0005] Further exacerbation is found in that the powder form has a
very large surface area enough to support water sucked in or
absorbed or volatile organics, and the volatile organics can be
released during heating and can cause gas and particulates to be
thrown outward from the deposition source toward the substrate.
Similar considerations pertain to materials which are melted before
vaporization and form droplets erupted to the substrate
surface.
[0006] These unwanted particulates or droplets may result in
unacceptable defects in products, particularly in electronic or
optical products, dark spots may appear in images, or shorts or
opens may result in failures within electronic devices.
[0007] Organic deposition apparatuses have been proposed to heat
the organic powder more uniformly and to prevent the bursts of
particulates or droplets from reaching the substrate. Many designs
for complicated baffling structures between the source material and
the vapor efflux aperture have been suggested to ensure vapor
exits.
[0008] FIG. 1 is a schematic sectional view showing the inner
structure of a conventional apparatus for depositing an organic
electroluminescent layer, and shows a deposition source 10 mounted
in a vacuum chamber 13 of the deposition apparatus and a substrate
12 located above the deposition source 10. The substrate 12 to be
coated with the organic electroluminescent layers is mounted to an
upper plate 13-1 of the chamber 13, and the deposition source 10 to
have a deposition material 20 (organic material) is mounted on a
thermally insulating structure 14 fixed to a bottom wall 13-2' of
the chamber 13.
[0009] FIG. 2a is a sectional view showing the inner structure of
the deposition source shown in FIG. 1, and shows that a baffle 11B
is provided in the deposition source 10 to prevent particulates or
droplets contained in the vapor of the deposition material 20 from
directly exiting through a vapor efflux aperture 11C formed on the
top plate 11A of the deposition source 10. The baffle 11B
corresponds to the vapor efflux aperture 11C and is fixed to a
number of support rods 11B-1 fixed to the top plate 11A of the
deposition source 10 to maintain certain space from the top plate
11A.
[0010] The deposition apparatus using the deposition source 10 with
the above structure has a heater or a heating means on (or under)
the top plate 11A, or is constructed for the top plate 11A to have
a heater in order to transfer heat to the deposition material 20
located around the center away from the side wall 11D. Thus, the
heat generated at the side wall 11D as well as from the top plate
11A is transferred directly to the deposition material 20 so that
the deposition material 20 is heated and vaporized. The vapor of
vaporized deposition material 20 is moved along the surface of the
baffle 11B and deposited on the substrate 12 (in FIG. 1) after exit
through the vapor efflux aperture 11C.
[0011] FIG. 2b is a sectional view showing the change of distance
between the top plate of the deposition source in FIG. 1 and the
deposition material after the deposition is processed for a certain
amount of time. Thus, FIG. 2b shows a state that the distance
between the top plate 11A and the surface of the deposition
material 20 is increased.
[0012] As explained above, the quantity of the deposition material
20 received in the deposition source 10 is decreased gradually by
heating and vaporizing reactions in progressing the deposition
process also the thickness of the deposition material 20 is
decreased. Thus, in a certain amount of time, the initial distance
(A in FIG. 2a) between the top plate 11A and the surface of the
deposition material 20 in the deposition source is remarkably
increased (a in FIG. 2b).
[0013] Due to increase of the distance between the top plate 11A
and the surface of the deposition material 20, the heat transfer
path is increased so that the deposition rate (that is,
vaporization rate of the deposition material) set at the initial
stage is decreased. Thus, in order to maintain the initially-set
deposition rate, the temperature of the top plate 11A acting as the
heater heating the deposition material 20 is needed.
[0014] In particular, while the deposition process is progressed,
the distance between the top plate 11A and the surface of the
deposition material 20 is increased. Under this situation, the
sufficient heat generated at the top plate 11A cannot reach the
deposition material 20, and so the deposition material located on
the center is not vaporized though the heat generated from the side
wall 11D is supplied. Consequently, if the input amount of the
deposition material 20 is high (that is, the thickness of the
deposition material 20 is high), it is difficult to expect that all
the deposition material is vaporized.
[0015] Also, the distance between the substrate 12 and the
deposition material 20, which is directly related to the uniformity
of deposition layer, is increased to result in change of the
deposition characteristics in time.
[0016] Low molecule organic electroluminescent material contains a
large amount of organic material unstable to heat, and causes a
problem of lowering the characteristics of the organic
electroluminescent material by inducing resolution or change of the
material characteristics due to excessive radiant heat in the
deposition process. In addition, additional processes for cooling
the chamber, exhausting the vacuum pressure, and re-vacuumizing are
required to supply new deposition material to replenish the
exhausted deposition material because the deposition process is
conducted under high vacuum condition. Such additional processes
cause loss of the process time.
[0017] In order to solve these problems, it is desirable to
maintain uniformly the initial deposition characteristics (for
example, vaporization rate of the deposition material) in supplying
more deposition material in the deposition source at a time.
[0018] On the other hand, in the deposition source 10 with the
structure shown in FIG. 2a and FIG. 2b, the side wall 11D acts as a
heating unit (for example, structure which coils are wound around
the side wall 11D). As shown in FIG. 1, however, since the sidewall
11D is exposed to the exterior, the thermal efficiency is lowered
because all heat generated at the side wall 11D is not transferred
to the deposition material 20 and some heat is radiated to the
exterior.
[0019] In addition, as describe above, in progressing the
deposition process, the deposition material 20 supplied in the
deposition source 10 is consumed, and so the thickness of the
deposition material 20 is decreased. Thus, heat is generated at the
sidewall 11D corresponding to the portions without the deposition
material and is not transferred directly to the deposition
material, which contributes to energy waste.
[0020] Another drawback of the deposition source 10 is that the
heat generated at the top plate 11A and the side wall 11D is not
sufficiently transferred to the deposition material 20 located at
the lower portion of the deposition source 10, that is, the
deposition material 20 adjoining the surface of the bottom wall
11E. As a result, all of the deposition material 20 is not heated
and vaporized. Particularly, depending on positions within the
deposition source 10, the temperature of each deposition material
20 becomes different, that is, thermal gradient within the
deposition source. Therefore, it is difficult to form a uniform
deposition layer on the substrate.
SUMMARY OF THE INVENTION
[0021] An object of the present invention is to provide the
deposition source which can compensate change of the distance
between the heating means and the surface of the deposition
material caused by decrease of the thickness of the deposition
material according to consumption of the deposition material in the
deposition process for the purpose of solving problems caused by
increase of the distance between the top plate (heating means) of
the deposition source and the surface of the deposition material
supplied into the deposition source from the deposition
process.
[0022] Another object of the present invention is to provide the
deposition source which can enhance thermal efficiency through
preventing heat generated at the heating means from exiting to the
exterior by adding a heat-cutting function.
[0023] Further, another object of the present invention is to
provide the deposition source for forming organic
electroluminescent layers which can obtain a uniform deposition
layer by minimizing factors of temperature change and by
efficiently using all the deposition material through supplying
heat to the deposition source adjoining the surface of the bottom
wall.
[0024] The deposition source according to the present invention is
installed in a chamber, heated by applied electric power to
transfer heat to a vapor deposition material received therein and
applying a vaporized deposition material generated therein to a
substrate to form deposition organic electroluminescent layers onto
the substrate, and comprises a vessel consisted of a top plate on
which a vapor efflux aperture is formed, a side wall, and a bottom
wall; a heating means for supplying heat to the deposition material
received in the vessel, the heating means being capable of moving
vertically; and a means for moving said heating means, the moving
means being operated in response to the signal of a sensing means
on varied distances between the heating means and the surface of
said deposition material. Thus, the heating means is moved downward
by the moving means to maintain the distance between the heating
means and the surface of the deposition material at an
initially-set value when the thickness of the deposition material
is decreased.
[0025] Another deposition source according to the present invention
is installed in a chamber, to form deposition organic
electroluminescent layers onto the substrate, by applying a
vaporized deposition material generated therein to a substrate, by
transferring heat to a vapor deposition material received therein,
heated by applied electric power, and comprises a vessel consisted
of a top plate on which a vapor efflux aperture is formed, a side
wall, and a bottom plate, the bottom plate being capable of moving
vertically; a heating means for supplying heat to the deposition
material received in the vessel; and a means for moving said bottom
plate, the moving means being operated in response to the signal of
a sensing means on varied distances between the heating means and
the surface of the deposition material. Thus, the bottom plate is
moved upward by the moving means to maintain the distance between
the heating means and the surface of the deposition material and
the distance between the substrate to be coated and the surface of
the deposition material at an initially-set value when the
thickness of the deposition material is decreased.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The present invention will be more clearly understood from
the detailed description in conjunction with the following
drawings.
[0027] FIG. 1 is a schematic sectional view of a conventional
apparatus for depositing an organic electroluminescent layer.
[0028] FIG. 2a is a sectional view showing the structure of the
deposition source shown in FIG. 1 prior to performing the
deposition process;
[0029] FIG. 2b is a sectional view showing change of the distance
between the top plate of the deposition source and the deposition
material in FIG. 1 after the deposition process is performed for a
certain period of time.
[0030] FIG. 3a is a sectional view of the deposition source
according to the first embodiment of the present invention.
[0031] FIG. 3b is a detailed view of part 3b in FIG. 3a.
[0032] FIG. 3c is a view showing relationship between the top plate
of the deposition source and the deposition material after the
deposition process is completed.
[0033] FIG. 4 is a sectional view of the deposition source
according to the second embodiment of the present invention.
[0034] FIG. 5 is a sectional view of the deposition source
according to the third embodiment of the present invention.
[0035] FIG. 6 is a sectional view taken along line 6-6 in FIG.
5.
[0036] FIG. 7 is a schematic perspective view showing relationship
between the substrate and the deposition source according to the
fourth embodiment.
[0037] FIG. 8a is a plane view of the substrate showing the initial
state which the electroluminescent layer is deposited on the
surface using the deposition source shown in FIG. 7.
[0038] FIG. 8b is a plane view of the substrate showing the state
that deposition of the electroluminescent layer has been completed
under the state that the deposition source (or substrate) shown in
FIG. 7 has been moved.
[0039] FIG. 9a and FIG. 9b are schematic sectional views showing
various shapes of the deposition source according to the fourth
embodiment of the present invention.
DETAILED DESCRIPTON OF THE INVENTION
[0040] Reference should be made to the drawings. The same reference
numerals are used throughout the drawings to designate same or
similar elements.
First Embodiment
[0041] FIG. 3a is a sectional view of the deposition source
according to the first embodiment of the present invention. A
deposition source 100 according to the first embodiment is a vessel
consisted of a top plate 101, a side wall 102, and a bottom wall
103. The deposition source 100 contains solid organic
electroluminescent vapor deposition material 20 (hereinafter,
referred to as "deposition material"). A vapor efflux aperture 101A
is formed on the top plate 101. The function of the vapor efflux
aperture 101A is to discharge vapor of vaporized deposition
material from the deposition source 100. A baffle member 104 fixed
to a lower surface of the top plate 101 corresponds to the efflux
aperture 101A.
[0042] The top plate 101 can act as a heating means (heater) for
supplying heat to the deposition material 20 or a separate heating
means can be placed on (or below) the top plate 101. In the
description below, a case where the top plate 101 acts as a heating
means will be explained as an example.
[0043] The most important feature of the first embodiment as shown
in FIG. 3a is that the top plate 101 of the deposition source 100
can be vertically moved. A movement means 151 to move the top plate
101 is mounted to the top plate 101.
[0044] The movement means 151 used in the deposition source 100
according to the first embodiment is a hydraulic or pneumatic
cylinder. Two support brackets 154 fixed a the side wall of the
chamber (13 in FIG. 1) are extended above the deposition source
100, and the cylinders 151 are mounted to each end portion of the
brackets 154. Rods 152 of each cylinder 151 are fixed to both sides
of the top plates 101, and therefore, each cylinder 151 does not
have any effect on vapor efflux of the deposition material 20
through the aperture 101A of the top plate 101.
[0045] On the other hand, each cylinder 151 is controlled by a
control means which is not shown in FIG. 3a, and the control means
is connected to a sensing means 153 (for example, optical sensor)
installed on the lower surface of the baffle 104 so that the
control means can control each cylinder 151 according to a signal
from the sensing means 153.
[0046] FIG. 3b is a detailed view showing part 3b in FIG. 3a. FIG.
3b shows partially the structure of the side wall 102 and the top
plate 101 which can be vertically moved along the side wall 102 of
the deposition source 100.
[0047] A number of vertical grooves 102-1 are formed on the inner
surface of the side wall 102, and protrusions 101-1 are formed on
the outer circumference surface of the top plate 101. Each
protrusion 101-1 corresponds to each groove 102-1 and can be
received in the corresponding groove 102-1 when the top plate 101
and the side wall 102 are assembled. Thus, when the top plate 101
is moved vertically, each protrusion 101-1 is moved along the
corresponding groove 102-1. Consequently, the top plate 101 can be
moved smoothly in the vertical direction without any deviation to
the side wall 102 from the initial location.
[0048] FIG. 3c is a view showing relationship between the top plate
of the deposition source and the deposition material after the
deposition process is completed. The function of the deposition
source constructed as described above will be explained in
reference to FIG. 3a and FIG. 3c.
[0049] As explained above, in the depositing process, the quantity
of the deposition material 20 received in the deposition source 100
is decreased gradually by the heating and vaporizing action. Thus,
the distance between the surface of the deposition material 20 and
the top plate 101 is changed (increased). The sensing means 153
mounted on the lower surface of the baffle 104 senses this change
of the distance between the surface of the deposition material 20
and the top plate 101, and then transmits the sensed signal to the
control means.
[0050] The control means calculates the distance between the
surface of the deposition material 20 and the top plate 101 (that
is, sum of the distance between the surface of the deposition
material 20 and the sensing means 153, and the distance between the
lower surface of the baffle 104 and the top plate 101) on the basis
of the signals transmitted from the sensing means 153, and then
compares the calculated distance with the initially-set distance
(value).
[0051] As a result of the above comparison, if the distance between
the surface of the deposition material 20 and the top plate 101 is
changed, the control means operates each cylinder 151. By operating
each cylinder 151, the rods 152 of each cylinder 151 are extended
downward so that the top plate 101 fixed to the ends of the rods
152 is moved downward along the side wall 102.
[0052] If the distance between the surface of the deposition
material 20 and the top plate 101 becomes the same as the
initially-set distance (A in FIG. 3a) by downward movement of the
top plate 101, that is, when the distance between the surface of
the deposition material 20 and the top plate 101 calculated by the
control means on the basis of the signals transmitted from the
sensing means 153 becomes the same as the initially-set distance,
the control means halts the operation of each cylinder 151.
[0053] The downward movement of the top plate 101 caused by the
control means and each cylinder 151 is continued during the
deposition process. After vaporizing all of the deposition material
20, the control means makes the rods 152 of each cylinder 151
return to the initial state as shown in FIG. 3a. Then, the top
plate 101 of the deposition source 100 returns to its initial
position, and thereafter, new deposition material is supplied to
the deposition source 100.
[0054] On the other hand, FIG. 3a and FIG. 3c show that the optical
sensor 153 acting as the sensing means is installed on the lower
surface of the baffle 104, but the optical sensor 153 can be
installed at any position including the lower surface of the top
plate 101 as long as the optical sensor 153 does not hinder the
deposition process and can sense the distance between the surface
of the deposition material 20 and the top plate 101.
Second Embodiment
[0055] FIG. 4 is a sectional view of the deposition source
according to the second embodiment of the present invention. The
entire structure of a deposition source 200 according to this
embodiment is the same as that of the deposition source 100 shown
in FIG. 3a and FIG. 3c. In this embodiment, a top plate 201 can act
as a heating means (heater) for supplying heat to the deposition
material 20 or a separate heating means can be placed on (or below)
the top plate 201. In the description below, a case where the top
plate 201 acts as a heating means will be explained as an
example.
[0056] The most important feature of the deposition source 200
according to the second embodiment is that a bottom plate 203 can
be moved vertically in response to change of the distance between
the surface of the deposition material 20 and the top plate
201.
[0057] As described above, the uniformity of the deposition layer
to be formed on the surface of the substrate (12 in FIG. 1) depends
on change of the distance between the substrate 12 and the
deposition material 20. In the deposition source 100 shown in FIG.
3a, change of the distance between the top plate 101 and the
deposition material 20 can be compensated by the vertical movement
of the top plate 101, but a means to adjust change of the distance
between the substrate 12 and the deposition material 20 is not
disclosed.
[0058] In order to compensate change of the distance between the
substrate 12 and the deposition material 20, the deposition source
200 according to this embodiment has the structure which the bottom
plate 203 can be moved vertically along a side wall 202.
[0059] A movement means 251 for moving the bottom plate 203 is
mounted under the bottom plate 203 on which the deposition material
20 is located. The movement means used in the deposition source 200
according to the second embodiment is a hydraulic or pneumatic
cylinder. The cylinder 251 is installed on a bottom wall 13-2 of
the chamber 13 shown in FIG. 1, a rod 252 of the cylinder 251 is
passed through the bottom wall 13-2, and the end of the rod 252 is
fixed to the lower surface of the bottom plate 203. However, the
structure shown in FIG. 4 is merely an example, and so the cylinder
having another structure can be installed.
[0060] In the this embodiment, the cylinder 251 is controlled by a
control means which is not shown in FIG. 4, the control means is
connected to a sensing means 253 (for example, optical sensor) so
that the control means controls the cylinder 251 according to the
signal transmitted from the sensing means 253.
[0061] On the other hand, a number of vertical grooves are formed
on the inner surface of the side wall 202, and a number of
protrusions are formed on the outer circumference surface of the
bottom plate 203. Each protrusion corresponds to each groove and
can be received in the corresponding groove. Therefore, the bottom
plate 203 can be moved smoothly in the vertical direction without
any deviation to the side wall 202 from the initial location. This
structure of the second embodiment is the same as that of the first
embodiment as shown in FIG. 3c except difference of the member on
which the protrusions are formed. Therefore, a further detailed
description on the protrusions and grooves is omitted.
[0062] In the depositing process, the quantity of the deposition
material 20 received in the deposition source 200 is decreased
gradually by the heating and vaporizing actions. Thus, the distance
between the substrate (12 in FIG. 1) and the deposition material 20
is increased (surely, the distance between the surface of the
deposition material 20 and the top plate 201 is also increased, and
the increased distance between the surface of the deposition
material 20 and the top plate 201 is the same as the increased
distance between the substrate 12 and the surface of the deposition
material 20).
[0063] The sensing means 253 mounted to a lower surface of a baffle
204 senses change of the distance between the surface of the
deposition material 20 and the top plate 201, and then transmits
the sensed signal to the control means. The control means
calculates the distance between the surface of the deposition
material 20 and the top plate 201 on the basis of the signals
transmitted from the sensing means 253, and then compares the
calculated distance with the initially-set distance.
[0064] As a result of the above comparison, if the distance between
the surface of the deposition material 20 and the top plate 201 is
changed, the control means operates the cylinder 251 installed
under the bottom plate 203. By operating of the cylinder 251, the
rod 252 of the cylinder 251 is extended upward so that the bottom
plate 203 fixed to the end of the rod 252 is moved upward along the
side wall 202.
[0065] If the distance between the surface of the deposition
material 20 and the top plate 201 becomes the same as the
initially-set distance (A in FIG. 3a) by the upward movement of the
bottom plate 203, that is, when the distance between the surface of
the deposition material 20 and the top plate 201 calculated by the
control means on the basis of the signals transmitted from the
sensing means 253 becomes the same as the initially-set distance,
the control means halts the operation of the cylinder 251.
[0066] The upward movement of the bottom plate 203 caused by the
control means and the cylinder 251 is continued during the
deposition process. After vaporizing all of the deposition material
20, the control means makes the rod 252 of the cylinder 251 return
to the initial state. Then, the bottom plate 203 of the deposition
source 200 returns to its initial position, and thereafter, new
deposition material is supplied to the deposition source 200.
[0067] On the other hand, FIG. 4 shows that the optical sensor 253
acting as the sensing means is installed at the lower surface of
the baffle 204, but the optical sensor can be installed at any
positions including the lower surface of the top plate 201 as long
as the optical sensor 253 does not hinder the deposition process
and can sense the distance between the surface of the deposition
material 20 and the top plate 201.
[0068] In the deposition sources 100 and 200 according to the first
and second embodiments as described above, when the thickness of
the deposition material 20 caused by consumption thereof during the
deposition process is changed, the distance between the surface of
the deposition material 20 and the top plate 101 (the first
embodiment) or the distance between the surface of the deposition
material 20 and the substrate 12 (the second embodiment) can be
maintained at the initially-set distance by the movement of the top
plate 101 (the first embodiment) or the bottom plate 203 (the
second embodiment). Thus, an appropriate amount of heat is
transferred to the deposition material 20 during the deposition
process so that the deposition temperature of the deposition
material 20 can be maintained uniformly and the optimum deposition
rate can be maintained.
[0069] In the second embodiment, especially, the distance between
the top plate 201 and the deposition material 20 as well as the
optimum distance between the substrate and the deposition material
are always maintained, and so it is possible to form a uniform
deposition layer. Also, the deposition material adjoining the
surface of the bottom plate 203 can be vaporized so that it is
possible to minimize the residual of the deposition material.
[0070] In particular, in a case where the deposition material is
supplied to the maximum, all of the deposition material can be
vaporized, and the time loss caused by vacuuming, heating, and
cooling processes to be performed in the deposition chamber after
replenishing the deposition material can be minimized. Therefore,
the second embodiment enables the depth of the deposition source to
make deeper than the conventional depositional source, and so the
quantity of the deposition material supplied to the deposition
source can be maximized.
Third Embodiment
[0071] FIG. 5 is a sectional view of the deposition source
according to the third embodiment of the present invention. The
deposition source 300 according to this embodiment has a vessel
consisted of a top plate 301 acting as the heating means, a side
wall 302, and a bottom wall 303. The structure of the top plate
301, on which a vapor efflux aperture 301A is formed and to which a
baffle member 304 is fixed, is the same as the top plates 101 and
201 of the deposition sources 100 and 200 of the first and second
embodiments, respectively. Therefore, a further detailed
description thereon is omitted.
[0072] The important aspect of the deposition source 300 shown in
FIG. 5 is that a number of coils C1, C2, . . . Cn as a heating
means for transferring heat to the deposition material 20 are wound
around the side wall 302, and a casing 350 is located at the outer
side of the side wall 302.
[0073] A number of coils C1, C2, . . . Cn are wound on the outer
circumference surface of the side wall 302. The uppermost coil C1
coincides with the surface of the deposition material 20 received
in the deposition source with the maximum height (thickness), and
the lowermost coil Cn coincides with the surface of the bottom wall
303.
[0074] The coils C1, C2, . . . Cn are arranged for electric power
to be individually applied thereto. A control means (not shown)
controls the electric power applied to each coil C1, C2, . . . Cn,
and the control means is connected to a sensing means 353 (for
example, optical sensor) which is mounted to the interior of the
deposition source.
[0075] The function of the coils C1, C2, . . . Cn arranged and
described as above is as follows.
[0076] In the early stage of the deposition process, the surface of
the deposition material 20, which is supplied into the deposition
source 20 with the maximum height, coincides with the uppermost
coil C1. At this time, electric power is applied to only the
uppermost coil C1, not the other coils C2, . . . Cn, by the control
means. The upper side of the deposition material 20 is heated and
vaporized by the heat generated at the top plate 301 acting as a
heating means and by the heat generated at the uppermost coil
C1.
[0077] In the depositing process, the quantity of the deposition
material 20 received in the deposition source 200 is decreased
gradually by the heating and vaporizing action (that is, decrease
of the height of the deposition material 20).
[0078] The sensing means 353 mounted on the lower surface of the
baffle 304 senses change of the height of the deposition material
20, and transmits the sensed signal to the control means. Then, the
control means calculates the height of the deposition material 20
on the basis of the signals transmitted from the sensing means 353.
According to the calculated height of the deposition material 20,
the control means controls the electric power applied to the other
coils C1, C2, . . . Cn.
[0079] That is, when the height of the deposition material 20 is
reduced and the surface of the deposition material 20 corresponds
to the second coil C2 positioned below the uppermost coil C1, the
control means blocks the electric power applied to the uppermost
coil C1 and applies the electric power to the second coil C2.
[0080] In succession, if the surface of the deposition material 20
corresponds to the lowermost coil Cn, the control means applies the
electric power to the lowermost coil Cn and blocks the electric
power applied to the other coils C1, C2 . . . .
[0081] As described above, in the depositing process, even though
the height of the deposition material 20 is changed, any one coil
to which the electric power is applied always corresponds to a
portion of the deposition material 20 to which the heat generated
by the top plate 301 is transferred. Therefore, it is possible to
prevent the heat generated by the coils C1, C2, . . . Cn from
transferring unnecessarily to the portion of the deposition
material which heating and vaporizing do not take place and the
deposition material is not present.
[0082] On the other hand, the casing 350 located at the outer side
of the side wall 302 prevents the heat generated at each coil C1,
C2, . . . Cn from radiating outward. Thus, most of the heat
generated at each coil C1, C2, . . . Cn is transferred to the
deposition material 20 through the side wall 302 so that it is
possible to minimize heat loss. Particularly, if the space formed
between the side wall 302 and the outer casing 350 is filled with a
thermal insulation material, the heat radiation is prevented more
effectively to minimize thermal gradient in the entire system. The
reference numeral 350A indicates the opening formed on the casing
350 for connecting power lines to the coils C1, C2, . . . Cn.
[0083] More excellent adiabatic property can be obtained by forming
the casing 350 with oxide or nitride of aluminum (Al), zirconium
(Zr), silicon (Si), yttrium (Y), etc., having high thermal
capacity.
[0084] Another feature of the deposition source according to this
embodiment is shown in FIG. 6. FIG. 6 is a sectional view taken
along the line 6-6 in FIG. 5 and shows a recess 303A formed at the
lower surface of the bottom wall 303 and a coil C received in the
recess 303A.
[0085] The recess 303A is formed to the longitudinal (or widthwise)
direction on the bottom wall 303, and consists of many linear
portions and connection portions connecting two neighboring linear
portions. Thus, the single coil C is spread on the entire surface
of the bottom wall 303. Both ends of the coil C are connected to
the power supply (not shown).
[0086] When the deposition process is performed, the electric power
is applied to any one of the coils C1, C2, . . . Cn wound around
the side wall 302 as well as the coil C received in the recess 303A
of the bottom wall 303 (surely, the electric power is applied to
the top plate 301 acting as a heating means). Therefore, the heat
generated at the coil C received in the recess 303A of the bottom
wall 303 is transferred to the deposition material adjoining the
surface of the bottom wall 303.
[0087] In the deposition source according to third embodiment as
described above, in the processing the depositing process, even
though a height of the deposition material is changed, the coil to
which the electric power is applied is always corresponded to a
portion of the deposition material to which heat generated by the
top plate is transferred. Therefore, it is possible to prevent heat
generated by the coils from transferring unnecessarily to a portion
of the deposition material which is not heated and vaporized and a
portion of the deposition source in which the deposition material
is not present.
[0088] Also, the casing provided at the exterior of the side wall
prevents the heat generated at the coils mounted to the side wall
from radiating outward, and so most generated heat is transferred
to the deposition material through the side wall to minimize
thermal gradient in the entire system.
[0089] In addition, when an additional coil is provided at the
bottom wall of the deposition source, sufficient heat can be
transferred to the deposition material which is remotely located
from the heating means (that is, the deposition material adjoining
the surface of the bottom wall), and so all of the deposition
material can be used effectively and a uniform deposition layer can
be obtained.
Fourth Embodiment
[0090] FIG. 7 is a schematic perspective view showing relationship
between the deposition source according to the fourth embodiment
and the substrate. An inner structure of the deposition source 400
is not shown in FIG. 7.
[0091] The deposition source 400 according to this embodiment is
consisted of a top plate 401 with certain length and width, a side
wall 402, and a bottom wall. A vapor efflux aperture 401A is formed
on the top plate 401. An organic electroluminescent vapor
deposition material is received in the space formed by the top
plate 401, the side wall 402, and the bottom wall.
[0092] A feature of this embodiment is to constitute the deposition
source 400 whose effective deposition length (that is, length A of
the vapor efflux aperture 401A of the top plate 401 actually
contributing to the deposition process) is longer than, or the same
as, the width b of the substrate 12 on which the electroluminescent
layer is formed.
[0093] FIG. 8a is a plane view of the substrate showing the initial
state that the electroluminescent layer is formed on the surface of
the substrate by means of the deposition source 400 shown in FIG.
7. If the deposition source 400 as described above is used for
forming the electroluminescent layer on the surface of the
substrate 12, the deposition material's vapor is diffused through
the apertiure 400A of the top plate 401, and then dispersed and
deposited uniformly on the surface of the substrate 12 over the
entire width.
[0094] The more effective deposition process can be performed by
moving the deposition source 400 constructed as described above or
the substrate 20 to the longitudinal direction of the substrate.
That is, when the deposition source 400 or the substrate 20 is
moved horizontally (linearly) to the arrow direction shown in FIG.
8, the electroluminescent layer as shown in FIG. 8a is continuously
deposited on the surface of the substrate 12 over the entire
length. Ultimately, as shown in FIG. 8b showing the surface of the
substrate on which the deposition of the electroluminescent layer
is completed after moving horizontally the deposition source 400 or
the substrate 12, the uniform electroluminescent layer is formed on
the entire surface of the substrate 12.
[0095] On the other hand, each respective deposition source 100,
200, 300 and 400 described in the first to fourth embodiments has
the inner space divided into the lower and upper portion, and the
cross sectional surface of the lower portion is the same as that of
the upper portion. Therefore, the flow rate of vapor of the
deposition material at the lower portion is practically equal to
the flow rate at the upper portion. Also, due to the large surface
area of the upper portion of the deposition source, heat loss of
the deposition material in the inner space is increased. In order
to eliminate the above drawbacks, the present invention modified
the shape of the deposition source.
[0096] FIG. 9a to FIG. 9d are sectional views of the deposition
sources, and show various shapes of the deposition source according
to the present invention. Another feature of the deposition sources
500A, 500B, 500C, and 500D according to the present invention is
that the sectional surface area of the upper portion at which the
aperture is formed is smaller than that of the lower portion.
[0097] Though the sectional surface areas in a tube can be
different in different positions, the quantity of flow is same
anywhere in the tube, and therefore, the flow rate of a portion
having smaller sectional surface area is higher than that of
another portion having larger sectional surface area.
[0098] Consequently, just before diffusing vapor of the deposition
material through the aperture, the flow rate of vapor at the upper
portion having smaller sectional surface area is higher than that
of vapor at the lower portion of the deposition source. Higher flow
rate induces increase of the vapor's kinetic energy (molecules of
the vaporized deposition material), and so the density and
uniformity of the deposition layer formed on the substrate can be
enhanced. Also, since the sectional surface area of the upper
portion through which the vapor of the deposition material is
diffused is small, heat loss outward can be minimized and the
deposition source is not influenced by such exterior interference
as change of ambient temperature.
[0099] In the present invention, on the other hand, a material
having higher thermal capacity than quartz, for example, oxide or
nitride of aluminum (Al), zirconium (Zr), silicon (Si), or yttrium
(Y), or composite material of at least two above, is used as the
deposition source's material. The thermal capacity of these metal
oxide or nitride is larger than organic material used as the
deposition material (about 3:1), and therefore, the adiabatic
property of the deposition source can be improved.
[0100] The preferred embodiments of the present invention have been
described for illustrative purposes, and those skilled in the art
will appreciate that various modifications, additions, and
substitutions are possible, without departing from the scope and
spirit of the present invention as disclosed in the accompanying
claims.
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