Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Including integrally formed optical element
Reexamination Certificate
2001-03-30
2002-10-22
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Including integrally formed optical element
C257S059000
Reexamination Certificate
active
06468822
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a liquid crystal display (hereinafter referred to as LCD) of an active matrix type with a thin film transistor (hereinafter referred to as TFT) used for a switching element, and more specifically to a method for manufacturing an active matrix type liquid crystal display using TFT (TFT-LCD) with improved display characteristics and productivity by forming a TFT array substrate with little point defect and line defect through five photo-lithography processes also using a line material having low resistance for a gate line and a source line.
Electro-optic elements for a display using a liquid crystal are popularly applied to products with its thin element and low electric consumption being highly appreciated, as one of the flat panel displays alternative to CRT.
For an electro-optic element for display using a liquid crystal, there are a simple matrix type LCD and TFT-LCD which uses TFT as a switching element. The TFT-LCD which has characteristics superior to CRT or the simple matrix type LCD in terms of portability and display quality has been popularly commercialized as notebook-size personal computers and the like. Generally, a liquid crystal layer is interposed between a TFT array substrate and an opposite substrate in TFT-LCD. On the TFT array substrate, TFT is formed as an array. On the opposite substrate, a common electrode and a color filter are mounted. On the outside of this kind of TFT array substrate and the opposite substrate, a polarizer is provided, respectively, and in addition, on one side, a back light is provided. With this kind of construction, satisfactory color display can be obtained.
However, in the TFT-LCD, it is necessary to fabricate the TFT array substrate in which TFT is formed as an array on a glass substrate using a technique for preparing semiconductor, and a great number of processes are required. As a result, there are problems that various defects are likely to occur, yield is decreased, more manufacturing equipment is required and that manufacturing cost is increased thereby.
As a method for solving these problems, Japanese Unexamined Patent Publication No. 268353/1998 discloses a method for manufacturing an active matrix type liquid crystal display, in which TFT array substrate is prepared through five photo-lithography processes.
FIGS. 7
to
9
are cross-sectional illustrations of a principal portion of a conventional TFT array substrate disclosed in Japanese Unexamined Patent Publication No. 268353/1998 (indicating components on an insulating substrate), and
FIG. 3
is a plane explanatory view.
The cross-section of
FIG. 7
schematically shows the cross-sectional construction taken on line X—X of
FIG. 3
, while
FIGS. 8 and 9
schematically show the cross sectional constructions of a TCP terminal portion provided outside the display area, respectively. The TCP connects a signal potential source for supplying signal potential to be inputted to a gate line, a source line, an auxiliary capacity line and a common electrode of the opposite substrate, with the gate line, the source line, the auxiliary capacity line and the common electrode.
Referring to
FIGS. 7
to
9
and
FIG. 3
, numeral
1
denotes a gate electrode,
2
an auxiliary capacity electrode,
3
a gate insulating film,
4
a semiconductor active film,
5
an ohmic contact film,
6
a drain electrode,
7
a source electrode,
8
a passivation film,
9
a pixel contact hole,
10
a portion having auxiliary capacity (hereinafter referred to as “auxiliary capacity”),
11
an pixel electrode,
12
a first display portion lead-out line,
13
a first TCP connection electrode,
14
a first TCP terminal contact,
15
a first TCP connection range,
16
a second display portion lead-out line,
17
a second TCP connection electrode,
18
a second TCP terminal contact,
19
a second TCP connection range,
20
an auxiliary capacity line,
21
a gate line,
22
a source line and
23
a semiconductor active film and ohmic contact film.
The gate electrode
1
is an electrode which is a part of the gate line
21
or an electrode serving as a terminal which branches off from the gate line
21
to connect to each TFT. The auxiliary capacity electrode
2
is an electrode which branches off from the auxiliary capacity line
20
and part of which is extended to a position where the electrode overlaps the pixel electrode
11
. Between the auxiliary capacity electrode
2
and the pixel electrode
11
, the auxiliary capacity
10
is formed with a laminated film comprising a first insulating film (the gate insulating film
3
) and a second insulating film as a dielectric substance. The auxiliary capacity
10
is formed in electrically parallel to a liquid crystal capacity formed between the pixel electrode
11
and the common electrode via a liquid crystal. The semiconductor active film and ohmic contact film numbered as
23
in
FIG. 3
comprises two, upper and lower layers which are numbered as
4
and
5
in FIG.
7
.
This conventional technique discloses a method for manufacturing a TFT array substrate through five photo-lithography processes. As an effect, it is stated that since there is no case where the source line
22
and the source electrode
7
cross over the difference formed by the semiconductor active film and the ohmic contact film
23
within the display area, disconnection of the source line
22
and the source electrode
7
can be substantially eliminated. It is also stated that though the semiconductor active film with ohmic contact film
23
is left around the pixel electrode
11
, by constructing the pixel electrode, and each of the semiconductor active film with ohmic contact film
23
, and the source line
22
to be separated via the second insulating film (the passivation film
8
), it is possible to reduce a simple short-circuit between the source line
22
and the pixel electrode
11
due to inferior patterning of the semiconductor active film with ohmic contact film
23
and the source line
22
or a short-circuit caused by a resistance reduction of the semiconductor active film
4
due to a light irradiation.
However, according to a conventional technique disclosed in Japanese Unexamined Patent Publication No. 268353/1998,in case of using a low resistance line material (such as Al) for a metal thin film material of the gate line
21
and the source line
22
, an oxide layer will be formed between the part comprising the gate line
21
or the source line
22
, and the pixel electrode
11
electrically connected therewith. The oxide layer causes high contact resistance at each of the contact part of the gate line
21
, and the pixel electrode
11
or the contact part of the source line
22
, and the pixel electrode
11
. There arises a display defect. That is, it was impossible to prepare TFT-LCD by using a low resistance line material such as Al for a line material according to the above method.
SUMMARY OF THE INVENTION
The present invention relates to a method for manufacturing electro-optic elements including a first insulating substrate wherein a display pixel having a pixel electrode in which a TFT is electrically connected is formed as an array, a TFT array substrate wherein a gate line for sequentially scanning each TFT intersects at right angles a source line which provides a signal potential to the pixel electrode and a second insulating substrate having an opposite substrate on which a color filter and a common electrode are formed, wherein the TFT array substrate and the opposite substrate are affixed with a liquid crystal layer interposed in-between and polarizers are placed outside the TFT array substrate and the opposite substrate, respectively, comprising the steps:
(a) forming the above gate line and the gate electrodes of the TFT by patterning a first metal thin film by a first photolithography process after forming the first metal thin film on the first insulating substrate;
(b) patterning by dry etching a semiconductor active film and an ohmic contact film by a second phot
Inoue Kazunori
Ishiga Nobuaki
Maeda Yoichiro
Nakamura Nobuhiro
Advanced Display Inc.
Hoang Quoc
Nelms David
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