Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Including integrally formed optical element
Reexamination Certificate
2001-06-29
2004-04-20
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Including integrally formed optical element
C438S040000, C438S043000, C438S067000, C438S082000, C438S099000, C438S113000, C438S455000, C438S459000, C438S665000, C438S666000, C438S692000, C438S693000, C438S701000, C438S713000
Reexamination Certificate
active
06723576
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method for organic EL (electroluminescence) displays and to a disposing method for semiconductor elements.
2. Description of Related Art
An organic EL display which is provided with organic EL elements corresponding to pixels is anticipated to replace liquid displays in the future because the display performance is superior and thinner, lighter, more electrically efficient displays are available due to the fact that organic EL elements emit very brightly and emit spontaneously, direct current low voltage driving is possible, response is immediate, and light is emitted by a solid organic film.
In particular, an active-matrix type organic EL display using an active-matrix driving method can be adapted to multi-grading and large displays because of the high brightness and high resolution due to the fact that transistor and capacity are provided in each pixel.
An example of an active-matrix type organic EL display which has been proposed is shown in FIG.
19
. This drawing shows one pixel, and a driving element, etc., which are disposed around this one pixel. In this active-matrix type organic EL display, switching transistor
34
, driving transistor
37
, and capacity
36
are provided for each pixel
35
made of an organic EL element. These elements are connected to a driving circuit by way of signal line
31
, power supply line
32
, scanning line
33
, and capacity line
38
. Reference numeral
19
is an electrode of pixel
35
. The purpose of using plural transistors is to enhance the reliability by improving off-current, lowering the deterioration of characteristics caused by impressing a voltage on the transistor.
In this active-matrix type organic EL display, a pixel is selected by switching transistor
34
, then organic EL element as a pixel
35
emits at predetermined brightness by driving transistor
37
. As these transistors, use of a thin film transistor wherein an active layer is a low temperature polycrystal silicon film which can be formed on a glass base board is proposed in order to form an organic EL display on a large area of transparent base board.
Additionally, an organic EL display using the conductance control method (T. Shimoda, M. Kimura, et al., Proc. Asia Display 98, 217; M. Kimura, et al., IEEE Trans. Elec. Dev., 46, 2282 (1999); M. Kimura, et al., Proc. IDW99,171), the control of the intensity of brightness of an organic EL element is performed by changing the conductivity of electricity of a polycrystal silicon layer which forms the thin film transistor.
In an organic EL display using this method, there is a concern that the uniformity of emitted brightness is degraded due to the variability of the current supplied to the organic EL element because there is a variations in the characteristics of thin film transistor. In order to realize, for example, 256 gradations of brightness on a large area of a display by changing the current value in a thin film transistor, it is necessary to control the current value of the organic EL element within a precision of 0.5% by switching elements such as a thin film transistor. However, because the variability of the current value at the time of impressing of intermediate voltage is large in recent transistors in which the active layer is a low temperature polycrystal silicon thin film, it is therefore difficult to sufficiently control the brightness level at 256 levels.
In contrast, the variation of the characteristics of the transistors in which the active layer is a single crystal semiconductor is small; however, because such a transistor is usually manufactured in high temperature processes such as at 600° C. or higher, it is difficult to form such a transistor on the glass base board etc. which is currently usable as a large-area transparent base board. Also, translucent, single crystal semiconductor base board such as single crystal silicon base board cannot be used as a base board for organic EL display in which display transparency is required.
Also, in an active-matrix type organic EL display in
FIG. 19
, the aperture ratio is as small as 10% because the light from the organic EL element as a pixel
35
is blocked by four lines of wiring
31
to
33
, and
38
, two transistors
34
and
37
, and capacity
36
. Accordingly, in order to improve the aperture ratio of the active-matrix type organic EL display, it is necessary to decrease the area of the thin film transistor or the wiring.
Furthermore, regarding enlarging the display, the area of recent amorphous silicon transistor built-in active-matrix type liquid crystal display is 1 m×1 m at maximum. In an active-matrix type organic EL display, thin film transistors in which the active layer is a low temperature polycrystal silicon film is used; however, because the sizes of manufacturing devices such as vacuum devices is limited, a size such as 1 m×1 m is considered to be the maximum area as it is for the liquid crystal display.
On the other hand, in an organic EL display which is provided with a thin film transistor in which an active layer is a polycrystal silicon thin film, the thin film transistor and the organic EL element are manufactured in the following ways.
First of all, the thin film transistor is formed on a glass base board
11
by a process shown in
FIG. 20A
to FIG.
20
D.
As a manufacturing process for this thin film transistor, first of all, a film of amorphous silicon is formed on glass base board
11
by a PECVD method using SiH
4
and a LPCVD method using Si
2
H
6
. Consequently, this amorphous silicon is recrystallized to form polycrystal silicon film
12
by a laser irradiating method by using an excimer laser or a solid phase growing method.
FIG. 20A
shows this state. Consequently, after patterning this polycrystal silicon film
12
, gate insulation film
13
is formed, and gate electrode
14
is furthermore formed by film-forming and patterning.
FIG. 20B
shows this state.
Consequently, impurities such as phosphorus or boron are shot into the polycrystal silicon film
12
in a self-adjusting manner by using a gate electrode
14
. By doing this, source drain area
15
is formed on both sides of gate electrode
14
, and a CMOSFET is formed. Consequently, an insulating film
16
in the first layer is formed, and after making a contact hole on this insulating film, the source drain electrode
17
is formed by film-forming and patterning.
FIG. 20C
shows this state. Consequently, insulating film
18
in the second layer is formed, and after making contact hole on this insulating film, ITO electrode
19
(electrode for pixel) is formed by film-forming and patterning.
FIG. 20D
shows this state.
Consequently, as shown in
FIG. 21A
, adhesion layer
21
is formed on insulating layer
18
in the second layer, and an aperture part is formed in the pixel area on ITO electrode
19
(electrode for pixel). Consequently, layer
22
between the layers is formed on this adhesion layer
21
, and an aperture part is formed on the aperture part of cohesion layer
21
.
Consequently, by the plasma treatment using oxygen plasma or CF4 plasma etc., the wettability on the surface of aperture part on ITO electrode
19
(electrode for pixel) is improved. After that, positive hole injecting holes
23
which forms the organic EL element and light emitting layer
24
are formed in this aperture part. This layers are formed by a liquid phase process such as a spin coat method, a squeegee applying method, an ink jet method, or a spattering method, and a vacuum process such as a vacuum vaporization method. In Japanese Unexamined Patent Application, First Publication, No. Hei 10-12377, it is disclosed that the organic light emitting layer which is provided for emitting colors such as red, blue and green can be randomly patterned in each pixel by forming and disposing organic EL material by an ink jet method.
Consequently, as shown in
FIG. 21B
, after a metallic thin film is formed as cathode
25
on light emitting layer
24
, and cathode
25
is
Inoue Satoshi
Kimura Mutsumi
Nozawa Ryoichi
Harness, Dickey & and Pierce, P.L.C.
Isaac Stanetta
Niebling John F.
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