U.S. patent application number 11/581089 was filed with the patent office on 2007-10-18 for method of transferring a laminate and method of manufacturing a semiconductor device.
This patent application is currently assigned to Semiconductor Energy Laboratory Co., Ltd.. Invention is credited to Yuugo Goto, Junya Maruyama, Yumiko Ohno, Toru Takayama.
Application Number | 20070243352 11/581089 |
Document ID | / |
Family ID | 29267852 |
Filed Date | 2007-10-18 |
United States Patent
Application |
20070243352 |
Kind Code |
A1 |
Takayama; Toru ; et
al. |
October 18, 2007 |
Method of transferring a laminate and method of manufacturing a
semiconductor device
Abstract
An object of the present invention is to provide a method of
transferring an object to be peeled onto a transferring member in a
short time without imparting damage to the object to be peeled
within a laminate. Also, another object of the present invention is
to provide a method of manufacturing a semiconductor device in
which a semiconductor element manufactured on a substrate is
transferred onto a transferring member, typically, a plastic
substrate. The methods are characterized by including: forming a
peeling layer and an object to be peeled on a substrate; bonding
the object to be peeled and a support through a two-sided tape;
peeling the object to be peeled from the peeling layer by using a
physical method, and then bonding the object to be peeled onto a
transferring member; and peeling the support and the two-sided tape
from the object to be peeled.
Inventors: |
Takayama; Toru; (Atsugi,
JP) ; Goto; Yuugo; (Atsugi, JP) ; Maruyama;
Junya; (Ebina, JP) ; Ohno; Yumiko; (Atsugi,
JP) |
Correspondence
Address: |
ERIC ROBINSON
PMB 955
21010 SOUTHBANK ST.
POTOMAC FALLS
VA
20165
US
|
Assignee: |
Semiconductor Energy Laboratory
Co., Ltd.
Atsugi-shi
JP
|
Family ID: |
29267852 |
Appl. No.: |
11/581089 |
Filed: |
October 16, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10438854 |
May 16, 2003 |
7147740 |
|
|
11581089 |
Oct 16, 2006 |
|
|
|
Current U.S.
Class: |
428/40.1 ;
257/E21.122; 257/E21.567 |
Current CPC
Class: |
H01L 21/2007 20130101;
Y10T 428/14 20150115; H01L 21/76251 20130101; H01L 2221/68368
20130101 |
Class at
Publication: |
428/040.1 |
International
Class: |
B32B 33/00 20060101
B32B033/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 17, 2002 |
JP |
2002-143797 |
Claims
1. A peelable adhesive medium comprising: a first heat-peeling
adhesive and a second heat-peeling adhesive with a substrate
interposed therebetween.
2. A peelable adhesive medium according to claim 1, wherein the
peelable adhesive medium is a two-sided tape.
3. A peelable adhesive medium according to claim 1, the substrate
comprises a pair of substrates with a cured adhesive interposed
therebetween.
4. A peelable adhesive medium according to claim 1, wherein the
peelable adhesive medium is interposed between a support and an
object to be peeled.
5. A peelable adhesive medium comprising: a first
ultraviolet-peeling adhesive and a second ultraviolet-peeling
adhesive with a substrate interposed therebetween.
6. A peelable adhesive medium according to claim 5, wherein the
peelable adhesive medium is a two-sided tape.
7. A peelable adhesive medium according to claim 5, the substrate
comprises a pair of substrates with a cured adhesive interposed
therebetween.
8. A peelable adhesive medium according to claim 5, wherein the
peelable adhesive medium is interposed between a support and an
object to be peeled.
9. A peelable adhesive medium comprising: a heat-peeling adhesive
and an ultraviolet-peeling adhesive with a substrate interposed
therebetween.
10. A peelable adhesive medium according to claim 9, wherein the
peelable adhesive medium is a two-sided tape.
11. A peelable adhesive medium according to claim 9, the substrate
comprises a pair of substrates with a cured adhesive interposed
therebetween.
12. A peelable adhesive medium according to claim 9, wherein the
peelable adhesive medium is interposed between a support and an
object to be peeled.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of transferring a
laminate. In addition, the present invention relates to a method of
manufacturing a semiconductor device having a circuit structured by
semiconductor elements, typically thin film transistors, in which
an object to be peeled that contains the semiconductor elements is
transferred to a substrate. For example, the present invention
relates to an electro-optical device, typically a liquid crystal
module, a light emitting device, typically an EL module, or an
electronic device in which such a device is mounted as parts
thereof.
[0003] 2. Description of the Related Art
[0004] In recent years the focus has been on techniques of
structuring thin film transistors by using semiconductor layers
(having a thickness on the order of several nm to several hundreds
of nm) formed on a substrate having an insulating surface. The thin
film transistors are widely employed in electronic devices such as
ICs and electro-optical devices, and in particular, the development
of thin film transistors as switching elements of image display
devices has been accelerating.
[0005] Many different kinds of applications that utilize this type
of image display device have been anticipated, and the application
to portable devices particularly has taken center stage. Devices
that are lightweight, resistant to impact, and able to withstand
some amount of deformation are expected. Glass and quartz are often
used in thin film transistor substrates at present, and these
substrates have disadvantages in that they are heavy and they
easily break. Further, it is difficult to make large-size glass and
quartz substrates, and therefore they are unsuited to thin film
transistor substrates from the viewpoint of mass production. Trials
have consequently been performed for forming thin film transistors
on lightweight, durable plastic substrates, typically substrates
having flexibility such as plastic films.
[0006] However, the present situation is that plastic has a low
heat resistance, and therefore the maximum process temperature for
forming the thin film transistors must be lowered. As a result,
thin film transistors cannot be formed having electrical
characteristics that are as good as those of thin film transistors
formed on substrates having relatively high heat resistance, such
as glass substrates, and quartz substrates.
[0007] On the other hand, peeling methods for peeling an object to
be peeled, which exists on a substrate through a separation layer,
from the substrate have already been proposed. For example, the
techniques discussed in JP 10-125929 A (pages 4 to 10) and JP
10-125931 A (pages 6 to 10) are ones in which a separation layer
made from amorphous silicon (or crystalline silicon) is formed, and
air gaps are made to develop within the amorphous silicon (or the
crystalline silicon) by passing laser light through a substrate and
emitting hydrogen contained in the amorphous silicon. The substrate
is then peeled from the object to be peeled.
[0008] In addition, processes similar to the techniques of JP
10-125929 A and JP 10-125931 A are reported in JP 2002-217391 A
(pages 3 to 6, FIG. 9) for: forming a separation layer made from
amorphous silicon (or crystalline silicon); forming a second
substrate (temporary transferring member) on a surface of an object
to be peeled (stated as layer to be peeled in the official gazette,
typically indicating a thin film transistor) by using a
water-soluble temporary adhesive layer; irradiating laser light to
a separation interlayer insulating film through the substrate;
peeling a first substrate (glass substrate) from the object to be
peeled, and transferring the object to be peeled onto a third
substrate (film); immersing the third substrate within water, and
dissolving the water-soluble temporary adhesive layer; and peeling
the object to be peeled from the second substrate, thus exposing
the surface of the object to be peeled.
[0009] However, it is essential to use a substrate having good
light transmitting characteristics with the methods disclosed in JP
10-125929 A and JP 10-125931 A, and therefore there is a problem in
that the substrates capable of being used are limited. Further, a
relatively high-power laser light irradiation is necessary in order
to impart an energy sufficient to pass through the substrate and
cause hydrogen contained in the amorphous silicon to be emitted,
and therefore there is a problem in that the laser light may damage
the object to be peeled.
[0010] Further, if high-temperature heat treatment is performed in
an element manufacturing process when manufacturing elements on the
separation layer by the aforementioned methods, hydrogen contained
in the separation layer diffuses and is reduced, and there is a
concern that peeling cannot be sufficiently performed even if laser
light is irradiated to the separation layer.
[0011] In addition, the transferring member is fixed to the surface
of the object to be peeled using a curing adhesive, and therefore
the surface of the object to be peeled, for example, the surface of
the thin film transistor, specifically wirings or pixel electrodes
are not exposed when peeling the substrate from the object to be
peeled, and therefore it is difficult to measure the
characteristics of the object to be peeled after peeling off the
substrate. For cases of manufacturing a liquid crystal display
device or a light emitting device using an object to be peeled with
this type of structure, the structure becomes one in which a
plurality of substrates are bonded to one another, and the
thickness of the liquid crystal display device or the light
emitting device becomes larger, and there is a problem in that
electronic devices cannot be made smaller when using the liquid
crystal display device or the light emitting device. Further, there
is a problem in that projection light from a backlight in a liquid
crystal display device, and light emitted from light emitting
elements in a light emitting device each cannot be effectively
taken out.
[0012] The object to be peeled and the second substrate are bonded
by a water soluble adhesive in the invention disclosed in JP
2002-217391 A, but the surface area of the water soluble adhesive
that is exposed to water is small in actuality, and therefore there
is a problem in that peeling of the second substrate takes
time.
[0013] In addressing this problem, it is possible to shorten the
peeling time by removing a portion of the second substrate and
exposing a much larger surface area of the temporary adhesive
layer. The second substrate is disposable in this case, but there
is a problem in that costs will increase when using expensive
materials such as quartz glass, or rare materials in the second
substrate.
[0014] In addition, if an organic resin is used in an interlayer
insulating film of the thin film transistor, which is the object to
be peeled, there is a problem in that the volume of the interlayer
insulating film expands and the film deforms because organic resins
tend to absorb moisture, and thin film transistor wirings will peel
off.
SUMMARY OF THE INVENTION
[0015] The present invention has been made in view of the
above-mentioned problems, and an object of the present invention is
to provide a method of bonding onto a transferring member an object
to be peeled, which is peeled from a substrate in a short time
without damage being imparted to the object to be peeled within a
laminate.
[0016] According to the present invention, there is provided a
method of transferring a laminate including: forming a peeling
layer and an object to be peeled on a substrate; bonding the object
to be peeled and a support through a peelable adhesive medium;
peeling the object to be peeled from the peeling layer by using
physical means, and then bonding the object to be peeled onto a
transferring member; and peeling the support and a two-sided tape
from the object to be peeled.
[0017] Further, according to the present invention, there is
provided a method of transferring a laminate including: forming a
peeling layer and an object to be peeled on a substrate; bonding
the object to be peeled and a support through a peelable adhesive
medium; peeling the object to be peeled from the peeling layer by
using physical means, and then bonding one side of the object to be
peeled onto a first transferring member; peeling the support and
the peelable adhesive medium from the object to be peeled; and
bonding the other side of the object to be peeled to a second
transferring member.
[0018] Further, according to the present invention, there is
provided a method of manufacturing a semiconductor device
including: forming a peeling layer and an object to be peeled
including a semiconductor element on a substrate; bonding the
object to be peeled and a support through a peelable adhesive
medium; peeling the object to be peeled from the peeling layer by
physical means, and then bonding the object to be peeled onto a
transferring member; and peeling the support and the peelable
adhesive medium from the object to be peeled.
[0019] Further, according to the present invention, there is
provided a method of manufacturing a semiconductor device
including: forming a peeling layer and an object to be peeled on a
substrate; bonding the object to be peeled and a support, through a
peelable adhesive medium; peeling the object to be peeled from the
peeling layer by physical means, and then bonding one side of the
object to be peeled onto a first transferring member; peeling the
support and the peelable adhesive medium from the object to be
peeled; and bonding a second transferring member to the other side
of the object to be peeled.
[0020] Further, a semiconductor element is a thin film transistor,
an organic thin film transistor, an organic thin film transistor, a
thin film diode, a photoelectric conversion element, or a resistive
element. A photoelectric conversion element made through a silicon
PIN junction can be given as a typical example of the photoelectric
conversion element.
[0021] Further, the object to be peeled has an oxide layer
contacting the peeling layer, typically, a single layer made of a
silicon oxide or a metallic oxide, or a laminate structure
thereof.
[0022] Further, the peeling layer is a metallic film or a nitride
film. The metallic film or the nitride film includes a single layer
including an element selected from the group consisting of
titanium, aluminum, tantalum, tungsten, molybdenum, copper,
chromium, neodymium, iron, nickel, cobalt, ruthenium, rhodium,
palladium, osmium, and iridium, an alloy material mainly containing
the elements, or a nitride compound of the elements, or a laminate
structure thereof.
[0023] Further, an adhesive of the peelable adhesive medium is an
adhesive capable of being peeled by heat (hereinafter indicated as
heat-peeling adhesive) and/or an adhesive capable of being peeled
by ultraviolet light irradiation (hereinafter indicated as
ultraviolet-peeling adhesive).
[0024] Further, plastic can be given as a typical example of the
first transferring member, typically plastic having flexibility
like plastic film. Furthermore, materials having a poor waterproof
property (such as paper, cloth, woods, and metals applied to the
transferring member) can be used in the first transferring member.
Further, materials having thermal conductivity can also be
used.
[0025] Further, plastic, typically plastic having flexibility like
plastic film, can be given as a typical example of the second
transferring member. Furthermore, materials having a poor
waterproof property (such as paper, cloth, woods, and metals
applied to the transferring member) can be used in the first
transferring member. Further, materials having thermal conductivity
can also be used.
[0026] Further, typical examples of the physical means include
means that use human hand and wind pressure of a gas sprayed from a
nozzle, and means of peeling off by a relatively small force such
as ultrasound.
[0027] Note that a tape-shaped material in which an adhesive is
formed on both sides of a substrate (two-sided tape), a similar
sheet-shaped material (two-sided sheet), a similar film-shaped
material (two-sided film) and the like can be given as the peelable
adhesive medium. Although the present invention will be explained
below using two-sided tape as a typical example of the peelable
adhesive medium in embodiment modes and embodiments, two-sided
sheets and two-sided films may also be applied thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In the accompanying drawings:
[0029] FIGS. 1A to 1E are diagrams showing the concept of
Embodiment Mode 1 of the present invention;
[0030] FIGS. 2A to 2D are cross sectional diagrams showing a
process of manufacturing an active matrix substrate in accordance
with Embodiment 1 of the present invention;
[0031] FIGS. 3A to 3D are cross sectional diagrams showing the
process of manufacturing the active matrix substrate in accordance
with Embodiment 1 of the present invention;
[0032] FIGS. 4A to 4C are cross sectional diagrams showing the
process of manufacturing the active matrix substrate in accordance
with Embodiment 1 of the present invention;
[0033] FIGS. 5A and 5B are cross sectional diagrams showing the
process of manufacturing the active matrix substrate in accordance
with Embodiment 1 of the present invention;
[0034] FIGS. 6A and 6B are cross sectional diagrams showing a
peeling process and a transferring process, respectively, of the
active matrix substrate in accordance with Embodiment 1 of the
present invention;
[0035] FIGS. 7A and 7B are cross sectional diagrams showing a
process of manufacturing an EL module in accordance with Embodiment
2 of the present invention;
[0036] FIG. 8 is a top view of an EL module in accordance with
Embodiment 3 of the present invention;
[0037] FIGS. 9A and 9B are cross sectional diagrams showing a
process of manufacturing a liquid crystal module in accordance with
Embodiment 4 of the present invention;
[0038] FIG. 10 is a top view of a liquid crystal module in
accordance with Embodiment 5 of the present invention;
[0039] FIGS. 11A to 11F are diagrams showing the concept of
Embodiment Mode 2 of the present invention;
[0040] FIGS. 12A to 12F are diagrams showing electronic devices to
which Embodiment 6 of the present invention is applied;
[0041] FIGS. 13A to 13C are diagrams showing electronic devices to
which Embodiment 6 of the present invention is applied;
[0042] FIGS. 14A and 14B are graphs showing electrical
characteristics of TFTs manufactured in accordance with Embodiment
1 of the present invention; and
[0043] FIG. 15 is a photograph showing the EL module manufactured
in accordance with Embodiment 2 of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment Modes
[0044] Embodiment modes of the present invention are explained
below.
Embodiment Mode 1
[0045] Procedures of a typical transferring method using the
present invention are explained briefly using FIGS. 1A to 1E.
[0046] First, a description will be made with reference to FIG. 1A.
Reference numeral 10 denotes a substrate, reference numeral 11
denotes a peeling layer, reference numeral 12 denotes an oxide
layer, reference numeral 13 denotes an object to be peeled, and
includes the oxide layer 12.
[0047] Glass substrates, quartz substrates, ceramic substrates, and
the like can be used as the substrate 10. Further, silicon
substrates, metallic substrates, and stainless steel substrates may
also be used.
[0048] A peeling layer 11, which is a nitride layer or a metallic
layer, is formed on the substrate 10. A typical example of the
metallic layer includes a single layer made of an element selected
from the group consisting of titanium (Ti), aluminum (Al), tantalum
(Ta), tungsten (W), molybdenum (Mo), copper (Cu), chromium (Cr),
neodymium (Ne), iron (Fe), nickel (Ni), cobalt (Co), ruthenium
(Ru), rhodium (Rh), palladium (Pd), osmium (Os), and iridium (Ir),
or an alloy mainly containing the above elements, or a laminate
structure thereof. A typical example of the nitride layer is a
single layer made from a nitride of the above metal elements, for
example, titanium nitride, tungsten nitride, tantalum nitride, or
molybdenum nitride, or a laminate structure thereof.
[0049] The object to be peeled 13 that contains the oxide layer 12
is formed next on the peeling layer 11, which is a nitride layer or
a metallic layer. An oxide layer that uses silicon oxide, silicon
oxynitride, or a metal oxide may be formed as the oxide layer 12.
Note that the oxide layer 12 may be formed by using any film
formation method, such as sputtering, plasma CVD, coating, and the
like.
[0050] Semiconductor elements (such as thin film transistors,
organic thin film transistors, thin film diode photoelectric
conversion elements, resistive elements, and the like) may also be
included in the object to be peeled 13.
[0051] Next, a description will be made with reference to FIG. 1B.
One surface of a two-sided tape 14 is bonded onto the object to be
peeled 13. Two-sided tape applied with an ultraviolet-peeling
adhesive or a heat-peeling adhesive is used. Cracks are easily
generated in the object to be peeled 13 during a later peeling
process if air bubbles enter between the object to be peeled 13 and
the two-sided tape 14 at this point, and therefore bonding is
performed so that air bubbles do not enter between the object to be
peeled 13 and the two-sided tape 14. Note that, by using a tape
mounting apparatus or the like in this process, bonding can be
performed in a short time so that air bubbles do not enter between
the object to be peeled 13 and the two-sided tape 14.
[0052] The other side of the two-sided tape 14 is bonded to a
support 15. The support 15 may be a quartz glass, a metal, a
ceramic, or the like, for example. It is necessary to fix the
support 15 securely to the two-sided tape 14 at this point. This is
for preventing the support 15 and the two-sided tape 14 from
peeling off first when peeling the object to be peeled 13 from the
substrate 10. Note that the two-sided tape can be bonded to the
support in a short time by using a press machine or the like in
this process.
[0053] Next, a description will be made with reference to FIG. 1C.
The peeling layer 11 is peeled from the object to be peeled 13 by
applying a physical force to peeling layer 11, which is made from a
nitride layer or a metallic layer, and the oxide layer 12. An
example is shown here in which the mechanical strength of the
substrate is sufficient. If the adhesion between the peeling layer
11 and the oxide layer 12 is high, and the mechanical strength of
the substrate 10 is low, then there is a danger that the substrate
10 will crack during peeling. It is therefore possible to perform
more effective peeling if peeling is performed after a support (not
shown in the figures), for example plastic, glass, metal, ceramic,
or the like, is mounted to a rear surface of the substrate (the
surface on which the peeling layer is not formed).
[0054] Note that the physical force is a relatively small force
such as a manual force by a human hand, velocity pressure of a gas
sprayed from a nozzle, and ultrasound.
[0055] Next, a description will be made with reference to FIG. 1D.
The object to be peeled 13 is bonded to a transferring member 17 by
using an adhesive 16. Note that it is possible for the adhesive 16
to use an adhesive capable of being peeled off by a reaction
(hereinafter indicated as a reaction setting adhesive), an adhesive
capable of being peeled off by heat (hereinafter indicated as a
thermosetting adhesive), or adhesive capable of being peeled off by
light, such as an ultraviolet setting adhesive (hereinafter
indicated as a photosetting adhesive. Epoxy resin, acrylic resin,
silicon resin, and the like can be given as typical examples of
these.
[0056] Next, a description will be made with reference to FIG. 1E.
The object to be peeled 13 and the two-sided tape 14 are peeled
apart. If ultraviolet peeling two-sided tape is used for the
two-sided tape 14, peeling can be performed by irradiating
ultraviolet light for a short period of time, specifically for 50
to 100 seconds. Further, peeling can be performed by heating the
substrate if heat peeling two-sided tape is used for the two-sided
tape 14. The heating temperature in this case is set within a range
from 90 to 150.degree. C, preferably from 110 to 120.degree. C.,
and the amount of heating time is as short as two to three minutes.
The support 15 and the two-sided tape 14 are peeled apart first,
and then the object to be peeled 13 and the two-sided tape 14 are
peeled apart.
[0057] The object to be peeled can be transferred onto the
transferring member by the above steps. Note that a separation
substrate may also be mounted on the exposed object to be
peeled.
[0058] Note that the term transferring member as used in this
specification denotes an object to which the object to be peeled is
bonded after the substrate is peeled from the object to be peeled.
There are no limitations placed on the materials used in the
transferring member, and any material such as plastics, glasses,
metals, ceramics, and the like may be used. Similarly, the term
support as used in this specification denotes an object to which
the object to be peeled is bonded when peeling the substrate by the
physical means. There are no limitations placed on the materials
used in the support, and any material such as plastics, glasses,
metals, ceramics, and the like may be used. Further, there are no
limitations placed on the shapes of the transferring member or the
support, and they may have a flat surface, a curved surface,
flexibility, and a film shape. Furthermore, if light weight is
given the highest priority, it is preferable to use a film shape
plastic, for example, polyethylene terephthalate (PET),
polyethylene sulfide (PES), polyethylene naphthalate (PEN),
polycarbonate (PC), nylon, polyether ether ketone (PEEK),
polysulfone (PSF), polyether imide (PEI), polyacrylate (PAR),
polybutylene terephthalate (PBT), ARTON (manufactured by JSR
Corporation) which is made from norbornene resin having a polar
group, or the like. A film having thermal conductivity, such as
aluminum nitride, or aluminum oxynitride, may also be formed on a
surface of these plastics. Further, iron, copper, aluminum,
aluminum nitride, magnesium oxide, or the like may also be
dispersed within these plastics. It is possible for the
transferring member to absorb heat generated due to driving if
these types of plastics are used in the transferring member for
cases in which a semiconductor circuit that performs high speed
operation, such as a CPU, or a memory is formed on the object to be
peeled.
[0059] Further, there is no dipping process in the present
invention, and therefore materials that have a poor waterproof
property (such as paper, cloth, woods, and metals applied to the
transferring member) can also be used in the transferring member.
Further, resins having thermal conductivity can also be used. In
addition, it is also possible to use a semiconductor device (such
as a logic circuit, a memory, a driver circuit, a power source
circuit, or a switch), on which semiconductor elements are formed,
as the transferring member, and to transfer a separate
semiconductor device onto the transferring member. The
characteristics of each of the semiconductor devices can be
investigated in this case, and only those having superior
characteristics (devices that are not defective) can be laminated.
The overall yield can therefore be effectively increased.
Embodiment Mode 2
[0060] The structure of a peelable adhesive medium (two-sided tape
is employed as a typical example) used in a transferring process of
the present invention is explained here.
[0061] FIG. 11A and FIG. 11B are explained. The two-sided tape used
in the present invention is one in which a first substrate 502
having a first adhesive 510, and a second substrate 504 having a
second adhesive 503, are joined together by a cured adhesive 505.
Heat-peeling adhesives and/or ultraviolet-peeling adhesives can be
used in the first adhesive and in the second adhesive. Further,
adhesives that are peelable by the irradiation of light (visible
light, infrared light, and the like) (light peeling adhesives), and
adhesives that are peelable by a chemical reaction (reaction
peeling adhesives) can also be used as substitutes for the
ultraviolet-peeling adhesives and the heat-peeling adhesives.
[0062] A heat-peeling adhesive and an ultraviolet-peeling adhesive
are used as typical examples of adhesives in this embodiment mode.
Note that it is also possible to use other adhesives.
[0063] Note that the first adhesive 501 indicates an adhesive
bonded to a support 506, and the second adhesive 509 indicates an
adhesive bonded to an object to be peeled 507 in this embodiment
mode.
[0064] An example of using a heat-peeling adhesive in a first
adhesive 508, and using an ultraviolet-peeling adhesive in a second
adhesive 509 is shown in FIG. 11B, but there are no limitations
placed on this combination. An ultraviolet-peeling adhesive can
also be used in a first adhesive 510, and a heat-peeling adhesive
can also be used in a second adhesive 511, as in FIG. 11C.
[0065] In addition, in the first adhesive and the second adhesive,
they may also be used adhesives of the same adhesive type. An
example of using heat-peeling adhesives in a first adhesive 512 and
in a second adhesive 513 is shown in FIG. 11D, and two-sided tape
that uses ultraviolet-peeling adhesives in a first adhesive 514 and
in a second adhesive 515 is shown in FIG. 11E.
[0066] On the other hand, although two-sided tapes in which the
first substrate 502 and the second substrate 504 are bonded are
shown in FIGS. 11A to 11E, both sides of a first substrate 516 may
also have a heat-peeling adhesive 517 and/or an ultraviolet-peeling
adhesive 518, as in FIG. 11F.
[0067] Note that, although peelable adhesive mediums having
adhesives on both sides of one or more substrates are shown in this
embodiment mode, the peelable adhesive medium is not limited to
these. An adhesive medium of only a peelable adhesive can also be
applied to the present invention.
Embodiments
Embodiment 1
[0068] An embodiment of the present invention is explained using
FIGS. 2A to 6B. A method of transferring a laminate having a thin
film transistor to an object to be peeled is explained here. First,
a method of manufacturing a pixel portion on the same substrate
simultaneously with TFTs of driver circuits formed in the periphery
of the pixel portion is explained first.
[0069] A description will be made with reference to FIG. 2A. A
peeling layer 101, which is a nitride film or a metallic film, an
oxide layer 102, a silicon oxide film 103, which is a base film,
and an amorphous silicon film 104 are formed on a substrate 100,
and a solution 105 containing nickel is applied on the top.
[0070] A glass substrate is used as the substrate 100 in this
embodiment, but the substrate 100 is not limited to glass, and
quartz substrates, semiconductor substrates, metallic substrates,
ceramic substrates, and the like can also be used.
[0071] Further, if a metallic film is used in the peeling layer
101, a single layer made from an element selected from the group
consisting of titanium (Ti), aluminum (Al), tantalum (Ta), tungsten
(W), molybdenum (Mo), copper (Cu), chromium (Cr), neodymium (Ne),
iron (Fe), nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium (Rh),
palladium (Pd), osmium (Os), and iridium (Ir), or an alloy or
chemical compound mainly containing the above elements, or a
laminate thereof may be used in the peeling layer 101. On the other
hand, if a nitride film is used in the peeling layer 101, then a
single layer made from titanium nitride, tungsten nitride, tantalum
nitride, or molybdenum nitride, or a laminate thereof, may be used.
A 50 nm thick tungsten film formed by sputtering is used here.
[0072] Further, a single layer made from a silicon oxide or a metal
oxide having a thickness form 10 to 600 nm, preferably from 150 to
200 nm, or a laminate structure of these single layers, may be used
as the oxide layer 102. A silicon oxide layer having a film
thickness of 200 nm and formed by sputtering is used here. The
bonding force between the metallic layer 101 and the oxide layer
102 is strong with respect to heat treatment, film peeling and the
like are not caused, and peeling can be performed simply by
physical means within the oxide layer, at an interface between the
oxide layer and the metallic layer, or at an interface between the
oxide layer and the nitride layer.
[0073] Further, a silicon oxynitride film (composition ratios:
Si=32%, O=27%, N=24%, H=17%) having a film thickness of 10 to 200
nm (preferably 50 nm) and formed by plasma CVD with film formation
conditions in which a deposition temperature is 400.degree. C., and
material gas flow rates for SiH.sub.4 and N.sub.2O are 4 sccm and
800 sccm, respectively, is used as the base insulating layer
103.
[0074] The amorphous silicon film 104 is formed next having a film
thickness of 25 to 80 nm, 54 nm in this embodiment, by using plasma
CVD with a film formation temperature of 300.degree. C. and using
SiH.sub.4 as a film formation gas. Note that there are no
limitations placed on the semiconductor film material, and the
amorphous silicon film 104 may be formed by a known means (such as
sputtering, LPCVD, plasma CVD, or the like) using silicon, a
silicon germanium alloy (Si.sub.XGe.sub.1-X, where X=0.0001 to
0.02), or the like.
[0075] Further, the concentration of the nickel solution 105 may be
suitably regulated. A nickel acetate salt solution containing
nickel at 10 ppm by weight is used in this embodiment, and applied
onto the amorphous semiconductor film by using a spinner. A method
of adding nickel elements to the entire surface of the amorphous
silicon film by sputtering may also be used as a substitute for
application.
[0076] Next, a description will be made with reference to FIG. 2B.
The amorphous semiconductor film is crystallized by performing heat
treatment. In the heat treatment, there may be used electric
furnace heat treatment or irradiation of strong light. If heat
treatment is performed within an electric furnace, it may be
performed at a temperature of 500 to 650.degree. C. for 4 to 24
hours. Heat treatment (heating at 550.degree. C. for 4 hours) for
crystallization is performed here after heat treatment (heating at
500.degree. C. for 1 hour) for dehydrogenation, and a crystalline
silicon 106 film is obtained. Note that, although crystallization
of the amorphous semiconductor film is performed by heat treatment
using a furnace here, crystallization may also be performed by a
lamp annealing apparatus. Note also that, although a
crystallization technique that employs nickel as a metallic element
for promoting the crystallization of silicon is used here, another
known crystallization technique may also be used, for example,
solid state growth or laser crystallization.
[0077] A first laser light (XeCl, wavelength 308 nm) is irradiated
next in the air, or within an oxygen atmosphere, in order to repair
defects remaining within crystal grains and improve crystallinity
after removing an oxide film on a surface of the crystalline
semiconductor film by using hydrofluoric acid or the like. Excimer
laser light having a wavelength equal to or less than 400 nm, and
the second harmonic or the third harmonic of a YAG laser are used
as the laser light. Whichever laser light is employed, pulse laser
light having a repetition frequency on the order of 10 to 1000 Hz
is used. The laser light is condensed by an optical system to 100
to 500 mJ/cm.sup.2, and then scanned over the silicon film surface
while being irradiated with an overlap ratio of 90 to 95%. The
first laser light is irradiated in the air at a repetition
frequency of 30 Hz and an energy density of 393 mJ/cm.sup.2 here.
Note that an oxide film is formed on the surface by the first laser
light irradiation because it is performed in the air or within an
oxygen atmosphere. The oxide film is then removed by using diluted
hydrofluoric acid, and an extremely thin oxide film is then formed
on the surface by using aqueous ozone.
[0078] Doping of a minute amount of impurities (boron or
phosphorus) is performed next in order to control thin film
transistor threshold values (not shown in the figures). Ion doping
in which diborane (B.sub.2H.sub.6) is excited by a plasma without
separation of mass is used here. The doping conditions are as
follows: diborane diluted to 1% by hydrogen is introduced within a
chamber at a flow rate of 30 sccm, and an acceleration voltage of
15 kV is applied. Boron is thus added to the amorphous
semiconductor film on the order of a dosage of
1.times.10.sup.13/cm.sup.2.
[0079] Next, a description will be made with reference to FIG. 2C.
The surface of the amorphous semiconductor film is then processed
for 120 seconds by aqueous ozone, forming a barrier layer 107 made
from a 1 to 5 nm thick oxide film.
[0080] An amorphous silicon film 108 containing argon element,
which becomes a gettering site, is formed next on the barrier layer
107 by sputtering to have a thickness of 50 nm. The film formation
conditions may be suitably regulated, and sputtering is used in
this embodiment. The film formation pressure is set to 0.3 Pa, the
flow rate of argon gas is set to 50 sccm, the film formation
electric power is set to 3 kW, and the film formation temperature
is set to 150.degree. C. Note that the atomic concentration of
argon elements contained in the amorphous silicon film is from
3.times.10.sup.20/cm.sup.3 to 6.times.10.sup.20/cm.sup.3, and the
atomic concentration of oxygen is from 1.times.10.sup.19/cm.sup.3
to 3.times.10.sup.19/cm.sup.3 at the above conditions. Heat
treatment is then performed for 4 hours at a temperature of
550.degree. C. within an electric furnace, thus performing metallic
element gettering.
[0081] Next, a description will be made with reference to FIG. 2D.
The amorphous silicon film 108 containing argon element, as the
gettering sites, and using as an etching stopper the barrier layer
106 is next removed using NMD3 solution (an aqueous solution
containing 0.2 to 0.5% of tetramethyl ammonium hydroxide). The
oxide film barrier layer is then removed by using diluted
hydrofluoric acid.
[0082] Next, a description will be made with reference to FIG. 3A.
The surface of the crystalline semiconductor film obtained is
processed with aqueous ozone, forming an extremely thin oxide film
(not shown in the figures). A mask made form resist is formed
thereon and patterned, and the crystalline semiconductor film is
next etched into predetermined shapes, forming separated
semiconductor layers 121 to 124. The mask made from resist is then
removed.
[0083] An insulating film 125 that becomes a gate insulating film,
and which has silicon as its main constituent, is formed next after
cleaning the surface of the silicon film. A silicon oxynitride film
having a film thickness of 155 nm is formed by plasma CVD at a film
formation temperature of 400.degree. C. in this embodiment, using
SiH.sub.4 and N.sub.2O as film formation gasses at a gas flow rate
ratio of 4/800 sccm.
[0084] A first conductive film having a film thickness of 20 to 100
nm, and a second conductive film having a film thickness of 100 to
400 nm are laminated next on the gate insulating film. A tantalum
nitride (TaN) film 126 having a film thickness of 30 nm is
laminated on the gate insulating film, and a tungsten (W) film 127
having a film thickness of 370 nm is laminated on the tantalum
nitride (TaN) film, in that order.
[0085] The first conductive film and the second conductive film are
formed of an element selected from the group consisting of tantalum
(Ta), tungsten (W), titanium (Ti), molybdenum (Mo), aluminum (Al),
and copper (Cu), or an alloy or chemical compound mainly containing
the elements. Further, as the first conductive film and the second
conductive film, a semiconductor film, typically a polycrystalline
silicon film into which an impurity such as phosphorus has been
doped, and an alloy film made from silver, palladium, and copper
(AgPdCu alloy film) may also be used. Further, there are no
limitations placed on using a two layer structure, and a three
layer structure may also be used, for example, in which a tungsten
film having a film thickness of 50 nm, an alloy film of aluminum
and silicon (Al--Si alloy film) having a film thickness of 500 nm,
and a titanium nitride film having a film thickness of 30 nm are
laminated in order. Further, if a three layer structure is
employed, tungsten nitride may also be used as a substitute for
tungsten in a first conductive film, an alloy of aluminum and
titanium may also be used as a substitute for the alloy of aluminum
and silicon in a second conductive film, and a titanium film may
also be used as a substitute for the titanium nitride film in a
third conductive film. Furthermore, a single layer structure may
also be used.
[0086] Next, a description will be made with reference to FIG. 3B.
Masks 128 to 131 made from resist are formed by exposure to light
in a photolithography process, and a first etching process is
performed in order to form gate electrodes and wirings (not shown
in the figures); The first etching process is performed under first
and second etching conditions. An ICP (inductively coupled plasma)
etching method may be used for etching. Films can be etched to have
a desired tapered shape by suitably regulating the etching
conditions (such as the amount of electric energy applied to a coil
shape electrode, the amount of electric energy applied to a
substrate side electrode, the temperature of the substrate side
electrode, and the like) when using ICP etching. Note that chlorine
gasses, typically chlorine (Cl.sub.2), boron trichloride
(BCl.sub.3), silicon tetrachloride (SiCl.sub.4), carbon
tetrachloride (CCl.sub.4), and the like, fluorine gasses, typically
carbon tetrafluoride CF.sub.4), sulfur hexafluoride (SF.sub.6),
nitrogen trifluoride (NF.sub.3), and the like, and oxygen (O.sub.2)
can be suitably used as etching gasses.
[0087] Etching is performed under the first etching conditions in
this embodiment by using carbon tetrafluoride (CF.sub.4), chlorine
(Cl.sub.2), and oxygen (O.sub.2) as etching gasses, setting their
respective gas flow rates to 25/25/10 sccm, and introducing a 500 W
RF (13.56 MHz) power to a coil shape electrode at a pressure of 1.5
Pa, thus generating a plasma. A 150 W RF (13.56 MHz) electrode is
also introduced to a substrate side (sample stage), thus in effect
applying a negative self-bias voltage. Note that the size of the
electrode surface area on the substrate side is 12.5 cm.times.12.5
cm, and the size of the surface area of the coil shape electrode (a
quartz disk on which a coil is formed here) is a diameter of 25 cm.
The tungsten film is etched by the first etching conditions, and an
edge portion of the first conductive layer takes on a tapered
shape. The etching rate of the tungsten film at the first etching
conditions is 200.39 nm/min, and the etching rate of the tantalum
nitride film is 80.32 nm/min, and therefore the selection ratio of
tungsten to tantalum nitride is approximately 2.5. Further, the
tungsten taper angle becomes approximately 26.degree. under the
first etching conditions.
[0088] The etching conditions are next changed to the second
etching conditions without removing the masks 128 to 131 made from
resist. Etching is then performed for a period on the order of
approximately 15 seconds using carbon tetrafluoride (CF.sub.4) and
chlorine (Cl.sub.2) as etching gasses, setting their respective gas
flow rates to 30/30 sccm, and introducing a 500 W RF (13.56 MHz)
electrode to the coil shape electrode at a pressure of 1.5 Pa, thus
generating a plasma. A 10 W RF (13.56 MHz) electrode is also
introduced to the substrate side (sample stage), in effect applying
a negative self-bias. The tungsten film and the tantalum nitride
film are etched by a similar amount under the second etching
conditions, in which carbon tetrafluoride (CF.sub.4) and chlorine
(Cl.sub.2) are mixed. The etching rate of tungsten under the second
etching conditions is 58.97 nm/min, and the etching rate of
tantalum nitride is 66.43 nm/min. Note that the etching time may
also be increased by on the order of 10 to 20% in order to perform
etching without any residue remaining on the gate insulating
film.
[0089] First shape conductive layers 132 to 135, including first
conductive layers and second conductive layers (first conductive
layers 132a to 135a and second conductive layers 132b to 135b), are
thus formed by the first etching process. The insulating film 125
that becomes the gate insulating film is etched by an amount on the
order of 10 to 20 nm, and regions not covered by the first
conductive layers 131 to 134 become a thinned gate insulating film
136.
[0090] Next, a description will be made with reference to FIG. 3C.
A second etching process is performed next without removing the
masks 128 to 131 made from resist. Etching is performed here for a
period on the order of 25 seconds by using sulfur hexafluoride
(SF.sub.4), chlorine (Cl.sub.2), and oxygen (O.sub.2) as etching
gasses, setting their respective gas flow rates to 24/12/24 sccm,
and introducing a 700 W RF (13.56 MHz) electrode to the coil shape
electrode at a pressure of 2.0 Pa, thus generating a plasma. A 4 W
RF (13.56 MHz) electrode is also introduced to the substrate side
(sample stage) to sufficiently apply a negative self-bias. The
etching rate of tungsten (W) by the second etching process is 227.3
nm/min, and the selection ratio of tungsten to tantalum nitride
(TaN) is 7.1. The etching rate of the silicon oxynitride film as an
insulating film 136 is 33.7 nm/min, and the selection ratio of W to
the silicon oxynitride film is 6.83. The selection ratio to the
insulating film 136 is thus high when using sulfur hexafluoride
(SF.sub.6) in the etching gas, and therefore film reduction can be
suppressed.
[0091] Second conductive layers 137b to 140b are formed by the
second etching process. The taper angle of the second conductive
layers 137b to 140b, which are tungsten films, becomes
approximately 70.degree.. On the other hand, the first conductive
films are hardly etched at all, and become first conductive layers
137a to 140a. Further, the masks 128 to 131 made from resist become
masks 145 to 148 made from resist due to the second etching
process.
[0092] Next, a description will be made with reference to FIG. 3D.
A first doping process is performed after removing the masks 145 to
148 made from resist, and the state of FIG. 3D is obtained. The
doping process may be performed by ion doping or ion injection. The
conditions of ion doping are such that phosphorus (P) is doped with
a dosage of 5.times.10.sup.13/cm.sup.2 and an acceleration voltage
of 50 kV. As (arsenic) may also be used as a substitute for P
(phosphorus) as an impurity element that imparts n-type
conductivity. The first conductive films 131 to 134 and the second
conductive films 137 to 140 become masks with respect to impurity
elements imparting the n-type conductivity in this case, and first
impurity regions 141 to 144 are formed in a self-aligning manner.
The impurity element that imparts n-type conductivity is added to
the first impurity regions 141 to 144 at a concentration ranging
from 1.times.10.sup.16 to 1.times.10.sup.17/cm.sup.3. Regions
having the same concentration range as the first impurity regions
are referred to as n- regions here.
[0093] Note that, although the first doping process is performed in
this embodiment after removing the masks 145 to 148 made from
resist, the first doping process may also be performed without
removing the masks 145 to 148 made from resist.
[0094] Next, a description will be made with reference to FIG. 4A.
Masks 150 to 153 made from resist are formed, and a second doping
process is performed. The mask 150 is a mask that protects a
channel formation region of a semiconductor layer for forming a
p-channel TFT of a driver circuit, and regions in the periphery of
the channel formation region. The mask 151 is a mask that protects
a channel formation region of a semiconductor layer for forming one
n-channel TFT of the driver circuit, and regions in the periphery
of the channel formation region. The masks 152 and 153 are masks
that protect a channel formation region of a semiconductor layer
for forming a pixel region TFT, and regions in the periphery of the
channel formation region.
[0095] The ion doping conditions in the second doping process are
such that phosphorus (P) is doped at a dosage of
3.5.times.10.sup.15/cm.sup.2 and an acceleration voltage of 65 kV,
thus forming a second impurity region 155. An impurity element that
imparts n-type conductivity is added to the second impurity region
155 at a concentration range of 1.times.10.sup.20 to
1.times.10.sup.21/cm.sup.3. Regions having the same concentration
range as the second impurity region are referred to as n+ regions
here.
[0096] Next, a description will be made with reference to FIG. 4B.
The masks 150 to 153 made from resist are removed, a mask 158 made
from resist is newly formed, and a third doping process is
performed.
[0097] Third impurity regions 150 to 161 and fourth impurity
regions 162 to 164, in which an impurity element that imparts
p-type conductivity is added to semiconductor layers that form
p-channel TFTs, are formed by the third doping process in the
driver circuits.
[0098] Impurity element addition is performed so that an impurity
element imparting a p-type conductivity is added to the third
impurity regions 159 to 161 in a concentration range of
1.times.10.sup.20 to 1.times.10.sup.21/cm.sup.3. Note that,
although there are regions (n- regions) in the third impurity
regions 159 to 161 to which P (phosphorus) is added in the previous
process, the impurity element imparting the p-type conductivity is
added at a concentration 1.5 to 3 times that of the impurity
element imparting the n-type conductivity, and therefore the
conductivity type in the third impurity regions 159 to 161 becomes
p-type. Regions having the same concentration range as the third
impurity regions are referred to as p+ regions here.
[0099] Further, an impurity element addition is performed so that
an impurity element imparting a p-type conductivity is added to the
fourth impurity regions 162 to 164 in a concentration range of
1.times.10.sup.18 to 1.times.10.sup.20/cm.sup.3. Regions having the
same concentration range as the fourth impurity regions are
referred to as p-regions here.
[0100] The impurity regions having n-type conductivity or p-type
conductivity are thus formed in each of the semiconductor layers by
the above processes. Conductive layers 137 to 140 become TFT gate
electrodes.
[0101] Next, a description will be made with reference to FIG. 4C.
Heat treatment is performed at a temperature of 300 to 550.degree.
C. for 1 to 12 hours after forming a first passivation film 165
made from a silicon nitride film having a film thickness of 100 nm.
The semiconductor layers are thus hydrogenated. Heat treatment is
performed at 410.degree. C. for 1 hour within a nitrogen atmosphere
in this embodiment. This process is one of terminating dangling
bonds in the semiconductor layers by hydrogen contained in the
first passivation film 165.
[0102] A first interlayer insulating film 166 made from an
inorganic insulator or an organic insulator is formed on the first
passivation film next. Positive photosensitive organic resins and
negative photosensitive organic resins can be used as organic
insulators. A first opening portion having curvature can be formed
for cases of using a photosensitive organic resin if exposure
processing is performed by a photolithography process, and the
photosensitive organic resin is then etched. The formation of the
opening portion having curvature has an effect for increasing the
coverage of an electrode formed later. A photosensitive acrylic
resin film having a thickness of 1.05 .mu.m is formed for the first
interlayer insulating film in this embodiment. Patterning and
etching of the first interlayer insulating film are performed next,
forming the first opening portion having inner walls with a gentle
slope.
[0103] Note that positive photosensitive resins are colored brown,
and therefore it is necessary to perform decolorization of the
photosensitive organic resin after etching if a positive
photosensitive organic resin is used in the first interlayer
insulating film 166.
[0104] Further, if a film made from an inorganic insulator is used
in the first interlayer insulating film 166, a surface thereof may
also be leveled.
[0105] A second passivation film 180 made from a nitride insulating
film (typically a silicon nitride film or a silicon oxynitride
film) is formed next so as to cover the opening portion and the
first interlayer insulating film. A silicon nitride film is used in
the second passivation film in this embodiment. As the film
formation conditions, sputtering is performed at high frequency
discharge using a silicon target and using nitrogen gas as
sputtering gas. The pressure may be suitably set, and a pressure of
0.5 to 1.0 Pa, a discharge power of 2.5 to 3.5 KW, and a film
formation temperature within a temperature range of room
temperature (25.degree. C.) to 250.degree. C. may be used.
Degassing from the first interlayer insulating film, can be
controlled by forming the second passivation film made from a
nitride insulating film.
[0106] It is possible to prevent moisture from the substrate side
and gasses due to degassing from the first interlayer insulating
film from entering EL elements formed later by forming the nitride
insulating film on the first interlayer insulating film.
Deterioration of the EL elements can thus be suppressed. Further,
the nitride insulating film has an effect in making bonded
two-sided tape easy to peel off in the following peeling process,
and a process for removing remaining adhesive is not necessary, and
therefore process can be simplified.
[0107] Next, after performing exposure processing by using a
photolithography process, the second passivation film 180, the
first passivation film 165, and the gate insulating film 136 are
etched in order, forming a second opening portion. Dry etching or
wet etching may be used as an etching process at this point. The
second opening portion is formed by dry etching in this
embodiment.
[0108] After forming the second opening portion, a metallic film is
formed next on the second passivation film and in the second
opening portion. The metallic film is etched after light exposure
by a photolithography process, thus forming source and drain
electrodes 181 to 188, and wirings (not shown in the figures). As
the metallic film, a film made from an element selected from the
group consisting of aluminum (Al), titanium (Ti), molybdenum (Mo),
tungsten (W), and silicon (Si), or an alloy film made of these
elements is used. After laminating a titanium film, a titanium
aluminum alloy film, and a titanium film (Ti/Al--Si/Ti) having film
thicknesses of 100 nm, 350 nm, and 100 nm, respectively, and the
laminate is patterned into a desired shape through etching, thus
forming source electrodes, drain electrodes, and wirings (not shown
in the figures).
[0109] A pixel electrode 190 is formed next. Transparent conductive
films such as ITO, SnO.sub.2, and the like can be used for the
pixel electrode 190. In this embodiment, an ITO film with a
thickness of 110 nm is formed and etched into a desired shape, thus
forming the pixel electrode 190.
[0110] Note that, although the pixel electrode 190 is made into a
transparent electrode in this embodiment because a method of
manufacturing a transmitting (downward emission type) display
device is discussed, it is preferable to use a material having
superior reflectivity, such as a film having aluminum (Al), or
silver (Ag) as its main constituent, or a laminate structure of
these films, for the pixel electrode when manufacturing a
reflective (upward emission type) display device.
[0111] Next, a description will be made with reference to FIG. 5B.
Exposure processing is performed by a photolithography process
after forming a film made from an organic insulator on the second
passivation film, the source electrodes, the drain electrodes, and
the pixel electrode. A second interlayer insulating film 200 is
then formed by etching the film made from an organic insulator and
forming a third opening portion. Positive photosensitive organic
resins and negative photosensitive organic resins can be used as
the organic insulator. The second interlayer insulating film is
formed by using a photosensitive acrylic resin having a thickness
of 1.5 .mu.m, and then etched by wet etching in this
embodiment.
[0112] A third passivation film 315 is then formed on the second
interlayer insulating film 200, after which a fourth opening
portion is formed on the pixel electrode 190. Degassing that
develops from the second interlayer insulating film can be
suppressed by covering the second interlayer insulating film 200
with the third passivation film 315. It is effective to use a film
made from a nitride insulating film (typically a silicon nitride
film or a silicon oxynitride film) as the third passivation
film.
[0113] A driver circuit 201 composed of a p-channel TFT 195 and an
n-channel TFT 196, and a pixel portion 202 having a pixel TFT 197
and a p-channel TFT 198 can thus be formed on the same substrate.
An active matrix substrate A 203 is thus completed. A process for
peeling the glass substrate away from the active matrix substrate A
and transferring it to a plastic substrate is shown next.
[0114] Next, a description will be made with reference to FIG. 6A.
One surface of a two-sided tape 210 is bonded to the third
passivation film and the pixel electrode 190. There is a danger
that the tungsten film 101, which is a peeling layer, and the glass
substrate cannot be peeled uniformly from the active matrix
substrate A 203 if air bubbles enter between the two-sided tape 210
and the second interlayer insulating film 200 or the pixel
electrode 190 at this point, and therefore it is necessary to
perform bonding so that air bubbles are not introduced. Two-sided
tape having an ultraviolet-peeling adhesive on one side, and a
heat-peeling adhesive on the other side is used in this embodiment,
and the side having the ultraviolet-peeling adhesive is bonded to
the third passivation film 315 and the pixel electrode 190. Of
course, two-sided tape having ultraviolet-peeling adhesive on both
sides may be used.
[0115] Next, a support 211 is bonded to the other surface of the
two-sided tape 210 (the side having the heat-peeling adhesive). For
the support 211, quartz glass, metals, ceramics, and the like can
be used. Note that the two-sided tape 210 and the support 211 must
be securely fixed together. This is for preventing the support 211
and the two-sided tape from peeling apart when peeling the
substrate from the active matrix substrate A 203. Quartz glass is
used for the support 211 in this embodiment, and the surface of the
two-sided tape having the heat-peeling adhesive is bonded to the
quartz glass.
[0116] The metallic layer 101 and the glass substrate 100 are next
peeled away from the active matrix substrate by applying a physical
force to the nitride layer or metallic layer 101 and the layer 102
made from an oxide film. The active matrix substrate from which the
glass substrate 100 has been peeled away is denoted as an active
matrix substrate B 215. An example in which the mechanical strength
of the glass substrate 100 is sufficient is shown here. There is a
possibility that the glass substrate 100 will break if the adhesion
between the nitride layer or metallic layer 101 and the layer 102
made from an oxide film is strong, and the mechanical strength of
the glass substrate 100 is weak. It is therefore possible to
perform peeling more effectively if a support (not shown in the
figures), for example, plastic, glass, metal, ceramic, or the like,
is bonded to a rear surface of the glass substrate (surface on
which the TFTs are not formed) before peeling.
[0117] Next, a description will be made with reference to FIG. 6B.
The layer 102 made from an oxide film is bonded to a transferring
member 213 by using an adhesive 212. It is possible to use reaction
setting adhesives, thermal setting adhesives, or photosetting
adhesives such as ultraviolet setting adhesives as the adhesive
212, and epoxy resins, acrylic resins, silicon resins, and the like
can be given as typical examples thereof. An ultraviolet setting
adhesive is used for the adhesive 212, and polycarbonate film is
used for the transferring member 213 in this embodiment. The
bonding conditions may be suitably set, and the polycarbonate film
is fixed to the active matrix substrate by irradiating ultraviolet
light for 120 seconds while heating on a hotplate to a temperature
on the order of 50 to 100.degree. C.
[0118] The two-sided tape 210 and the support 211 are peeled away
from the active matrix substrate B 215 next. After initially
heating to a temperature of 90 to 150.degree. C., preferably 110 to
120.degree. C., the quartz glass substrate 211 is peeled away from
the two-sided tape 210. UV irradiation is performed for 60 seconds,
and the two-sided tape 210 is peeled away from the second
interlayer insulating film 200 and the pixel electrode 190.
[0119] Although this embodiment adopts the two-sided tape in which
an ultraviolet-peeling adhesive is used on the side of the object
to be peeled and a heat-peeling adhesive is used on the support
side, the adhesives are not limited to this combination. It is also
possible to use a two-sided tape in which a heat-peeling adhesive
is used on the object to be peeled, and a heat-peeling adhesive is
used on the support. Similarly, it is also possible to use
two-sided tape having only heat-peeling adhesives, and two-sided
tape having only ultraviolet-peeling adhesives. In addition, it is
also possible to use light peeling adhesives and reaction peeling
adhesives, and the respective peeling conditions may be suitably
set.
[0120] The thin film transistors can be transferred onto the
plastic substrate by the above processes.
[0121] Next, the voltage-current characteristics of the thin film
transistors transferred according to this embodiment are shown in
FIGS. 14A and 14B. Note that V.sub.ds (the voltage difference
between a source region and a drain region) is set to 1 V.
[0122] First, a description will be made with reference to FIG.
14A. FIG. 14A shows the electrical characteristics of the n-channel
TFTs. The electrical characteristics of the n-channel TFTs
transferred onto the plastic substrate show almost no change for
the electrical characteristics of the TFTs before the transfer,
that is, the electrical characteristics of the n-channel TFTs
formed on the glass substrate hardly change. It is thus understood
that the n-channel TFTs are transferred onto the plastic substrate
without developing defects thereof.
[0123] Next, a description will be made with reference to FIG. 14B.
FIG. 14B shows the electrical characteristics of the p-channel
TFTs. Similarly to FIG. 14A, the electrical characteristics of the
p-channel TFTs transferred onto the plastic substrate show no
change with the electrical characteristics of the TFTs before the
transfer, that is, the electrical characteristics of the p-channel
TFTs formed on the glass substrate hardly change. It is thus
understood that the p-channel TFTs are transferred onto the plastic
substrate without developing defects thereof.
[0124] It is thus possible to transfer thin film transistors formed
on a glass substrate onto a plastic substrate in a short time by
using two-sided tape having an ultraviolet-peeling adhesive or a
heat-peeling adhesive. Moreover, thin film transistors having
electrical characteristics equivalent to those of thin film
transistors manufactured on glass substrates can be manufactured on
plastic substrates.
[0125] Further, it is possible to peel away a quartz glass
substrate, which is a support, without causing any damage thereof
by using two-sided tape when peeling the object to be peeled, which
contains thin film transistors, from a glass substrate. The support
can thus be reused. A large reduction in cost can therefore be
achieved for cases in which expensive materials like quartz glass
are used for the support.
[0126] In addition, the surface of the object to be peeled is
exposed, and therefore it is possible to measure the electrical
characteristics of thin film transistors after transferring them to
a plastic substrate.
Embodiment 2
[0127] An example of making an El module provided with EL
(electro-luminescence) elements 316 formed on a plastic substrate
is explained in this embodiment. FIGS. 7A and 7B are used in the
explanation.
[0128] First, an active matrix substrate C 216 of FIG. 6B is
manufactured in accordance with Embodiment 1, and then an EL layer
313 is formed on the third passivation film 315 and the pixel
electrode 190. The EL layer 313 is generally structured by a
laminate of thin films, such as light emitting layers, charge
injecting layers, and charge transporting layers. Thin films made
from light emitting materials that emit light (fluoresce) through
singlet excitation (singlet compounds) and thin films made form
light emitting materials that emit light (phosphoresce) through
triplet excitation (triplet compounds) can be used as the EL layer.
Further, each layer of the EL layer 313 may be a thin film made
from an organic material solely, and may be a laminate structure of
a thin film made from an organic material and a thin film made form
an inorganic material. In addition, the organic material may be
high molecular weight or low molecular weight ones. Known materials
can be used for these organic materials and inorganic materials. As
film formation methods for each layer, known means are adopted. A
CuPc film having a film thickness of 20 nm, an .alpha.-NPD film
having a film thickness of 30 nm, an Alq.sub.3 film having a film
thickness of 50 nm, and a BaF.sub.2 film having a film thickness of
2 nm are laminated by evaporation in this embodiment, thus forming
the EL layer 313.
[0129] A cathode 314 is formed next on the EL layer 313, and in
addition, a fourth passivation film (not shown in the figures) is
formed on the cathode 314. For the cathode 314, a metallic thin
film containing an element belonging to Group 1 or Group 2 of the
periodic table may be used, and a metallic film in which 0.2 to
1.5% (preferably 0.5 to 1.0%) by weight of lithium is added to
aluminum is suitable due to its charge injecting characteristics
and the like. Note that the diffusion of lithium elements into the
thin film transistors is controlled by the first to fourth
passivation films with the present invention, and therefore the
lithium elements do not affect the operation of the thin film
transistors.
[0130] The EL element 316 is thus formed by the pixel electrode
190, the EL layer 313, and the cathode 314 through the above
processes.
[0131] The structure shown in FIG. 7A concerns a downward emission
light emitting device, and light emitted from the EL element passes
through the pixel electrode 190 and is emitted from the plastic
substrate 213 side.
[0132] On the other hand, by using a metallic film having
reflectivity as a substitute for the pixel electrode 190, and using
a metallic film having a small film thickness (preferably from 10
to 50 nm) in the cathode 314, light emitted form the EL element
passes through the cathode and is emitted. Metallic films made of
Pt (platinum) and Au (gold), which have high work functions, are
used as the metallic film having reflectivity in order to make the
metallic film function as an anode. A metallic film containing an
element belonging to Group 1 or Group 2 of the periodic table is
used in the cathode.
[0133] Light does not pass through the portion below the pixel
electrode with this type of upward emission light emitting device,
and therefore it is possible to form memory elements and resistive
elements, and there are no problems associated with the first
interlayer insulating film 166 being colored. Consequently, it is
also possible to achieve a high degree of freedom in design, and
further, to simplify the manufacturing processes.
[0134] Next, a description will be made with reference to FIG. 7B.
A third interlayer insulating film is formed on a fourth
passivation film. It is preferable that a surface of a third
interlayer insulating film 319 be further leveled after formation.
Note that it is not always necessary to form the third interlayer
insulating film 319.
[0135] An EL element is sealed by bonding an opposing substrate 318
thereto by using an adhesive layer 317. Plastics such as PES
(polyethylene sulfide), PC (polycarbonate), PET (polyethylene
terephthalate), and PEN (polyethylene naphthalate) can be used for
the opposing substrate. A polycarbonate film is used in this
embodiment. Note that it is necessary that the plastic substrate be
made of a material having light transmitting characteristics for
cases in which a metallic film having reflectivity is used as a
substitute for the pixel electrode 190, and a metallic film having
a small film thickness (preferably from 10 to 50 nm) is used as the
cathode 314. An epoxy resin is used as the adhesive layer 317, and
a polycarbonate film is used as the opposing substrate in this
embodiment. If substrates made from the same material are used for
the substrate 213, which is the transferring member, and the
opposing substrate 318, then their thermal expansion coefficients
are equal, and the substrate is unsusceptible to the influence of
stress strain due to temperature change.
[0136] Further, the transferring member 213 and the opposing
substrate 318 are divided into a desired shape as needed. Then, the
FPC (not shown in the figures) is bonded thereto by using a known
technique.
[0137] Next, a description will be made with reference to FIG. 15.
FIG. 15 is a photograph of an upper surface of an EL module
manufactured according to this embodiment. From this photograph, it
can be understood that an EL module manufactured on a plastic
substrate by the processes of this embodiment emits light. Further,
polycarbonate films are used in a transferring member for the EL
module and an opposing substrate, and therefore an extremely thin
EL module can be manufactured.
Embodiment 3
[0138] The structures of an EL module obtained according to
Embodiment 1 and Embodiment 2 are explained using the top view of
FIG. 8. The transferring member 213 in Embodiment 2 corresponds to
a plastic substrate 900.
[0139] FIG. 8 is a top view showing a module (hereinafter referred
to as EL module) having a light emitting device provided with an EL
element. A pixel portion 902, a source side driver circuit 901, and
a gate side driver circuit 903 are formed on a plastic substrate
900 (typically a plastic film substrate). The pixel portion and the
driver circuits can be manufactured by the above embodiments.
[0140] Further, reference numeral 918 denotes a sealing material,
and reference numeral 919 denotes a protective film. The sealing
material 918 covers the pixel portion and the driver circuit
portion, and the protective film 919 covers the sealing material.
Note that it is preferable to use a material that is as transparent
or semi-transparent as possible with respect to visible light as
the sealing material 918. Further, it is preferable that the
sealing material 918 be a material through which moisture and
oxygen pass as less as possible. The light emitting element can be
completely shut off from the outside by sealing it using the
sealing material 918 and the protective film 919. Substances from
the outside such as moisture and oxygen, which promote
deterioration such as oxidation in EL layer can thus be prevented
from entering. In addition, heat generated during driving can be
radiated when using a film that has thermal conductivity (such as
an AlON film, or an AlN film) as the protective film and a light
emitting device having high reliability can be obtained.
[0141] In addition, it is sealed with an opposing substrate (not
shown in the figure) using an adhesive material. There are no
particular limitations placed on the shape of the opposing
substrate and the shape of a support, and those having a flat
surface, those having a curved surface, those having flexibility,
and those having a film shape may be used. It is preferable that
the opposing substrate be made of the same material as the film
substrate 900, for example a plastic substrate, in order to
withstand deformation due to heat, external forces, and the
like.
[0142] Further, although not shown in the figure, circular
polarizing means, called a circular polarization plate and composed
of a retardation plate (.lamda./4 plate) or a polarization plate,
may also be provided on the substrate 900 in order to prevent the
background from being reflected therein by reflection from the
metallic layers used (a cathode and the like, in this case).
[0143] Note that reference numeral 908 denotes wirings for
transmitting signals input to the source side driver circuit 901
and the gate side driver circuit 903, and video signals and clock
signals from an FPC (flexible printed circuit) 909, which becomes
an external input terminal, are received therethrough. Further, the
light emitting device of this embodiment may adopt digital drive
and analog drive, and the video signals may be digital signals and
may be analog signals. Note that, although only an FPC is shown in
the figure, a printed wiring board (PWB) may also be attached to
the FPC. The category of the light emitting device defined in this
specification includes not only the light emitting device main
body, but also the ones in the form of the FPC and the PWB being
attached thereto. Further, although it is also possible to form a
complex integrated circuit (such as a memory, a CPU, a controller,
or a D/A converter,) on the same substrate as the pixel portion and
the driver circuits, it is difficult to manufacture them by using a
small number of masks. It is therefore preferable to mount an IC
chip provided with a memory, CPU, controller, D/A controller, and
the like by using a COG (chip on glass) method, a TAB (tape
automated bonding) method, or a wire bonding method.
[0144] An EL module having highly reliable thin film transistors
with good electrical characteristics can be manufactured on a
plastic substrate by the above processes. Further, an extremely
small size, lightweight EL module can be manufactured by using a
plastic film for the plastic substrate.
Embodiment 4
[0145] An example of manufacturing a liquid crystal module formed
on a plastic substrate is explained in this embodiment. FIGS. 9A
and 9B are used in the explanation.
[0146] First, a description will be made with reference to FIG. 9A.
After obtaining the active matrix substrate C 216 in the state of
FIG. 6B in accordance with Embodiment 1, an orientation film is
formed on the active matrix substrate C of FIG. 6B by using a known
technique within a temperature range which the substrate is capable
of withstanding. An orientation film 617 is then formed and a
rubbing process is performed, thus manufacturing an active matrix
substrate D 600.
[0147] Note that an element a601, an element b602, an element c603,
and an element d604 of FIG. 9A correspond to the p-channel TFT 195,
the n-channel TFT 196, the pixel TFT 197, and the p-channel TFT 198
of FIG. 6B, respectively. Note also that a known technique may be
used in order to level the surface of the active matrix substrate.
After forming source electrodes and drain electrodes 605 to 612,
and wirings (not shown in the figures), a second interlayer
insulating film is formed. In addition, a second opening portion is
formed, and the connection wiring 614 and pixel electrodes 615 and
616 are formed.
[0148] An opposing substrate 620 is prepared next. Plastics such as
PES (polyethylene sulfide), PC (polycarbonate), PET (polyethylene
terephthalate), and PEN (polyethylene naphthalate) can be used in
the opposing substrate. Color filters (not shown in the figures),
in which colored layers and light blocking layers are disposed
corresponding to each pixel, are formed on the opposing substrate
620. Further, a light blocking layer (not shown in the figures) is
also formed in a driver circuit portion. A leveling film (not shown
in the figures) is formed covering the color filters and the light
blocking layers. An opposing electrode 621 made from a transparent
electrode is formed next on the leveling film, an orientation film
622 is formed over the entire opposing substrate, and a rubbing
process is performed. These processes can be performed using known
techniques within a temperature range which the opposing substrate
is capable of withstanding.
[0149] The active matrix substrate D 600, on which a pixel portion
and driver circuits are formed, and the opposing substrate 620 are
next bonded by using a sealing material 624. A filler is mixed into
the sealing material, and the two substrates are bonded together
with a uniform gap due to the filler. A liquid crystal material 623
is then injected between both substrates and then completely sealed
by using a sealant (not shown in the figures). Known liquid crystal
materials may be used for the liquid crystal material.
[0150] If necessary, the active matrix substrate D 600 and the
opposing substrate 620 are sectioned into desired shapes. In
addition, a polarization plate (not shown in the figures) and the
like may be suitably formed by using known techniques. An FPC (not
shown in the figures) may also be bonded by using a known
technique.
[0151] Note that plastic substrates having flexibility, such as
plastic films, can be used for the plastic substrate 213 and for
the opposing substrate 620, provided that a structure is employed
in which a fixed thickness is maintained for the liquid crystal
display device.
[0152] An active matrix liquid crystal module having high
reliability and good electrical characteristics can thus be
manufactured. Plastic is used in the substrates, and therefore an
extremely lightweight liquid crystal module can be
manufactured.
Embodiment 5
[0153] The structure of the thus obtained liquid crystal module
based on Embodiments 1 and 4 is described with reference to the top
view in FIG. 10.
[0154] A pixel portion 704 is placed in the center of an active
matrix substrate 701. A source signal line driver circuit 702 for
driving source signal lines is positioned above the pixel portion
704. Gate signal line driver circuits 703 for driving gate signal
lines are placed in the left and right of the pixel portion 704.
Although the gate signal line driver circuits 703 are symmetrical
with respect to the pixel portion in this embodiment, the liquid
crystal module may have only one gate signal line driver circuit on
one side of the pixel portion. A designer can choose the
arrangement that suits better considering the substrate size or the
like of the liquid crystal module. However, the symmetrical
arrangement of the gate signal line driver circuits shown in FIG.
10 is preferred in terms such as operation reliability and driving
efficiency of the circuit.
[0155] Signals are inputted to the driver circuits from flexible
printed circuits (FPC) 705. The FPCs 705 are press-fit through an
anisotropic conductive film or the like after opening contact holes
in the interlayer insulating film and resin film and forming a
connection electrode 309 so as to reach the wiring lines arranged
in given places of the substrate 701. The connection electrode is
formed of ITO in this embodiment.
[0156] A sealing agent 707 is applied along a perimeter of the
substrate in the periphery of the driver circuits and the pixel
portion. Then, an opposite substrate 706 is bonded to the substrate
701 while a spacer formed in advance on the active matrix substrate
keeps the gap between the two substrates constant. A liquid crystal
element is injected through a portion that is not coated with the
sealing agent 707. The substrates are then sealed by a sealant 708.
The liquid crystal module is completed through the above steps.
[0157] Although all of the driver circuits are formed on the
substrate here, several ICs may be used for some of the driver
circuits.
[0158] As described above, an active matrix liquid crystal module
having high reliability, good electrical characteristics and light
in weight can be manufactured.
Embodiment 6
[0159] An active matrix substrate, a liquid crystal module and an
EL module using the active matrix substrate, which are shown in
Embodiments 1 to 5, can be applied to the display portions of
various electronic apparatuses.
[0160] Such electronic apparatuses can be given as a video camera,
a digital camera, a projector, a head-mounted display (goggle type
display), a car navigation system, a car stereo, a personal
computer, a mobile information terminal (such as a mobile computer,
a mobile telephone or an electronic book etc.) or the like.
Practical examples thereof are shown in FIGS. 12 and 13.
[0161] FIG. 12A shows a personal computer which includes a main
body 3001, an image input portion 3002, a display portion 3003, a
keyboard 3004 and the like. A compact and lightweight personal
computer can be completed by implementing the present
invention.
[0162] FIG. 12B shows a video camera which includes a main body
3101, a display portion 3102, a sound input portion 3103, operating
switches 3104, a battery 3105, an image receiving portion 3106 and
the like. A compact and lightweight video camera can be completed
by implementing the present invention.
[0163] FIG. 12C shows a mobile computer which includes a main body
3201, a camera portion 3202, an image receiving portion 3203, an
operating switch 3204, a display portion 3205 and the like. A
compact and lightweight mobile computer can be completed by
implementing the present invention.
[0164] FIG. 12D shows a goggle type display which includes a main
body 3301, a display portion 3302, arm portions 3303 and the like.
A compact and lightweight goggle type display can be completed by
implementing the present invention.
[0165] FIG. 12E shows a player using a recording medium on which a
program is recorded (hereinafter referred to as the recording
medium), and the player includes a main body 3401, a display
portion 3402, speaker portions 3403, a recording medium 3404,
operating switches 3405 and the like. This player uses a DVD
(Digital Versatile Disc), a CD and the like as the recording
medium, and enables a user to enjoy music, movies, games and the
Internet. A compact and lightweight recording medium can be
completed by implementing the present invention.
[0166] FIG. 12F shows a digital camera which includes a body 3501,
a display portion 3502, an eyepiece portion 3503, operating
switches 3504, an image receiving portion (not shown) and the like.
A compact and lightweight digital camera can be completed by
implementing the present invention.
[0167] FIG. 13A shows a mobile telephone which includes a main body
3901, a sound output portion 3902, a sound input portion 3903, a
display portion 3904, operating switches 3905, an antenna 3906 and
the like. A compact and lightweight mobile telephone can be
completed by implementing the present invention.
[0168] FIG. 13B shows a mobile book (electronic book) which
includes a main body 4001, display portions 4002 and 4003, a
storage medium 4004, operating switches 4005, an antenna 4006 and
the like. A compact and lightweight mobile book can be completed by
implementing the present invention.
[0169] FIG. 13C shows a display which includes a main body 4101, a
support base 4102, a display portion 4103 and the like. A compact
and lightweight display of the present invention can be completed
by implementing the present invention.
[0170] As is apparent from the foregoing description, the range of
applications of the invention is extremely wide, and the invention
can be applied to any category of electronic apparatuses having
semiconductor devices therein.
[0171] Effects as shown below can be obtained by implementing the
structure of the present invention.
[0172] The object to be peeled of the laminate can be transferred
from the substrate onto a transferring member, in particular onto a
plastic substrate.
[0173] Further, an object to be peeled having semiconductor
elements (such as thin film transistors, organic thin film
transistors, thin film diodes, photoelectric conversion elements,
and resistive elements) can be transferred onto a transferring
member, in particular onto a plastic substrate, in a short
time.
[0174] Further, it is possible to measure the characteristics of
various semiconductor elements, typically thin film transistors,
after peeling an object to be peeled from a substrate and
transferring it onto a plastic substrate.
[0175] In addition, after transferring an object to be peeled onto
a plastic substrate, a support formed on the object to be peeled is
peeled away, and therefore the thickness of a device having the
object to be peeled becomes smaller, and miniaturization of the
overall device can be achieved. The transmittivity of light emitted
from light emitting elements or a backlight can be increased if the
device is a downward emission light emitting device or a
transmissive liquid crystal display device.
[0176] In addition, it is possible to peel an object to be peeled
from a substrate without damaging a support, and the support can be
reused. A large reduction in cost can therefore be achieved if an
expensive material like quartz glass, or a rare material is used
for the support.
* * * * *