Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
1999-04-20
2002-10-15
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S138000, C349S122000, C349S158000
Reexamination Certificate
active
06466279
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device, more especially to the improvement of a process for preparing an active matrix wiring substrate involved in it.
BACKGROUND
FIG. 3
is a schematic view of a channel-etched TFT formed on an active matrix wiring substrate involved in a conventional liquid crystal display device. FIG.
3
(
a
) is a plan; FIG.
3
(
b
), a cross sectional view; and FIG.
3
(
c
), a fragmentary cross sectional view showing its terminal. Referring to FIG.
3
(
b
), a gate electrode
2
a
is formed on a transparent insulating substrate
1
. A gate insulating film
3
is formed to cover the gate electrode
2
a
. A semiconductive layer
4
is further formed thereon so as to overlie the gate electrode
2
a
. Source electrode
6
a
and drain electrode
7
are separated from each other on the central of the semiconductive layer
4
, and connected to the same semiconductive layer
4
through an interposed ohmic is etched to contact layer
5
. An area of the ohmic contact layer
5
disposed between the source and drain electrodes
6
a
and
7
leave it only between the semiconductive layer
4
and each of the source and drain electrodes
6
a
and
7
. Further, a passivation film
17
is formed thereon so as to cover the surface thereof. On the passivation film
17
, a transparent conductive film to provide a pixel electrode
9
is connected to the drain electrode
7
interposed with a contact through-hole
11
formed through the passivation film
17
.
Next, a process for preparing the active matrix wiring substrate shown in
FIG. 3
will be explained below in reference to FIG.
4
.
(A) A first patterning step is carried out in which a conductive layer made of Al, Mo, Cr or the like is deposited on a transparent insulating substrate made of glass or the like to a thickness of 100 to 200 nm with a sputtering apparatus, and then gate wire
2
b
, gate electrode
2
a
and gate terminal portion
2
c
which is to be connected to an outside signal processing substrate for displaying are formed by a photolithographic step.
(B) Next, a second patterning step is carried out in which a gate insulating film
3
made of silicon nitride or the like, a semiconductive layer
4
made of amorphous silicon and an ohmic contact layer
5
made of n
+
-type amorphous silicon are laminated successively in this order to a thickness of about 400 nm, about 300 nm and about 50 nm, respectively with a PCVD apparatus, and then the semiconductive layer
4
and ohmic contact layer
5
are patterned at the same time.
(C) Then, a third patterning step is carried out in which source electrode
6
a
, source wire
6
b
, drain electrode
7
and data side terminal portion
7
a
are formed by photolithographic processing after depositing Mo, Cr or the like to a thickness of about 150 nm with a sputtering apparatus so as to cover the gate insulating film
3
and ohmic contact layer
5
. Unnecessary part of the ohmic contact layer
5
is removed which is the part except a portion that is positioned under the source and drain electrodes
6
a
and
7
to form a channel part of a TFT.
(D) Thereafter, a forth patterning step is carried out in which an inorganic passivation film
17
of silicon nitride is formed to a thickness of about 100 to 200 nm with a PCVD apparatus so as to cover a back channel of the TFT, source electrode
6
a
, source wire
6
b
, drain electrode
7
and the terminal portions; a contact through-hole
11
is formed for bringing the drain electrode
7
into contact with a pixel electrode
9
; and unnecessary part of the passivation film
17
which is located on the data side terminal
7
a
portion and unnecessary parts of the gate insulating film
3
and the passivation film
17
which are located on the gate terminal
2
c
portion are removed.
(E) Finally, a fifth pattering step is carried out after forming a transparent conductive film which is to be changed into the pixel electrode
9
with a sputtering apparatus.
By the above explained five patterning steps, a liquid crystal display device having the active matrix wiring substrate shown in
FIG. 3
whose preparing steps are greatly reduced can be prepared.
However, the above conventional liquid crystal display device (hereinafter referred as to “prior art I”) requires screening of light by means of a black matrix provided on a CF substrate in order to inhibit the leak of light from the space between the gate wire
2
b
and the pixel electrode
9
and from the space between the source wire
6
b
and the pixel electrode
9
as shown in FIG.
3
(
a
). In order to avoid the problems concerning the accuracy in superimposing the CF substrate on the active matrix wiring substrate, the light screening region of the black matrix needs to have a large space. As a result, the aperture ratio of the liquid crystal display device becomes low. On this account, the prior art I has such a problem that the transmittance of the liquid crystal display device becomes low.
Japanese Patent Kokai-Publication JP-A-9-152625(1997) (hereinafter referred as to “prior art II”) discloses, as a means of increasing the aperture ratio, a process for overlapping the pixel electrode
9
with each of the wires and thereby removing the black matrix of the CF side.
FIG. 5
is a cross sectional view showing a channel protecting TFT on an active matrix wiring substrate of the prior art
2
. Referring to
FIG. 5
, the structure of the channel protecting TFT in the active matrix wiring substrate will be explained as follows. There are a transparent insulating substrate
1
and a gate electrode
2
a
which is provided thereon and connected to a gate wire
2
b
. They are covered with a gate insulating film
3
on which a semiconductive layer
4
is provided so as to overlie the gate electrode
2
a
. On the central part of the semiconductive layer
4
, a channel protecting layer
13
is provided. There is provided a n
+
-type Si layer which covers both terminals of the channel protecting layer
13
as well as a part of the semiconductive layer
4
and is divided into two pieces to provide source electrode
6
a
and drain electrode
7
. On the outside terminal of one piece of the n
+
-type Si layer which is to be the source electrode
6
a
, transparent conductive film
14
and metallic later
15
are provided in this order to form a source wire
6
b
of a two-layered structure. Similarly, on the outside terminal, other piece of the n
+
-type Si layer which is to be drain electrode
7
, transparent conductive film
14
and metallic later
15
are provided in this order. The transparent conductive film
14
is prolonged and connected to the pixel electrode
9
to form a connecting electrode. Further, there is provided an interlaminar insulating film which covers the TFT, the gate wire
2
b
, the source wire
6
b
and the connecting electrode. On the interlaminar insulating electrode, a transparent conductive film which is to be the pixel electrode
9
is provided and connected to the drain electrode
7
of the TFT by the transparent conductive film of the connecting electrode through a contact through-hole formed through the interlaminar insulating film.
These characteristic features of the liquid crystal display device of the prior art II reside in that the pixel can overlap the wires without increasing a capacity between the pixel electrode
9
and each of the wires to provide a liquid crystal display device having a large aperture ratio and thereby being capable of displaying a bright image by forming a low dielectric interlaminar insulating film thickly between the pixel electrode
9
and the source electrode
6
a
as well as between the pixel electrode
9
and source wire
6
b.
SUMMARY OF THE DISCLOSURE
However, there have been encountered various problems during the course of the investigations toward the present invention. Namely, the aforementioned prior art II requires 9 patterning steps including newly additional preparing steps for forming the interlaminar insulating film and for making the contact through-
NEC Corporation
Qi Mike
Sughrue & Mion, PLLC
Ton Toan
LandOfFree
Liquid crystal display device and process for producing same... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal display device and process for producing same..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display device and process for producing same... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2958409