Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Including integrally formed optical element
Reexamination Certificate
1998-11-25
2001-09-04
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Including integrally formed optical element
C438S029000
Reexamination Certificate
active
06284558
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an active matrix liquid-crystal display device with thin-film transistor (TFT) substrate and a method for making the same.
BACKGROUND OF THE INVENTION
A conventional active matrix liquid-crystal (hereinafter also referred to as ‘LC’) display device with thin-film transistor(TFT) substrate will be explained below, referring to FIG.
1
. This device, as shown in
FIG. 1B
, has the structure that a twist-nematic liquid-crystal layer
620
is sandwiched between a TFT substrate
630
and a color filter (CF) substrate
610
. The TFT substrate
630
has the structure that, on a TFT glass substrate
104
, a gate electrode
105
, gate insulating film
107
, a−Si layer
109
, n+a−Si layer
110
, a source electrode
112
and drain electrode
111
, a pixel electrode
631
, and passivation film
632
are formed in this order. As the passivation film
632
, SiN film of about 300 nm thick made by plasma CVD is typically used. On the other hand, the CF substrate
610
has the structure that a black matrix
612
, color layer
613
and an opposing electrode
614
are formed, in this order, on a CF glass substrate
611
.
In such an active matrix liquid-crystal display device as composed above, it is necessary to the black matrix
612
so as to shield light through a light-leaked region B. Therefore, by reason that it is necessary to estimate an overlap margin of this light-shielding part, a light-transmitted region A of the LC display panel is reduced. Thus, there is the problem that the transmissivity of the entire device is reduced.
So, means for enlarging the light-transmitted region, i.e., means for enhancing the aperture ratio is proposed, e.g., Japanese patent application laid-open No.9-152625 (1997). This device has, as show in
FIG. 2A
, the structure that the pixel electrode
631
, data line
602
and gate line
601
are overlapped. In such an active matrix liquid-crystal display as thus composed, it is necessary to form interlayer insulating film
701
by using a material with low permittivity and possible to thicken so as to reduce the overlap capacity of the pixel electrode
631
, data line
602
and gate line
601
. For example, used is interlayer insulating film where 2 to 4 &mgr;m thick positive type photosensitive acrylic resin with specific permittivity &egr;=3.0 is laminated on inorganic film of SiN conventionally used.
The method of making the interlayer insulating film
701
will be explained below, referring to
FIGS. 3A
to
3
D. Like conventional methods, SiN layer
102
of about 300 nm thick is laminated by plasma CVD, forming a contact hole
113
by patterning (
FIG. 3A
) . Then, after coating it with photosensitive acrylic resin, patterning is conducted by pre-baking, exposure and alkali-development (FIGS.
3
B and
3
C). Then, UV light including i line is radiated all over the surface to decolorize into transparent film. Then, the resin is hardened by thermal cross-linking reaction. Then, transparent film such as ITO is formed by sputtering, patterned into the pixel electrode
631
(FIG.
3
D). Finally, it is annealed at 250° C. for about 30 min.
In the active matrix liquid-crystal display device with TFT substrate thus obtained, there is no light-leaked region, and therefore the black matrix is not necessary. Therefore, the numerical aperture can be enhanced.
However, in the conventional method, the layer formation and patterning are conducted for each of the SiN layer and organic film. Also, after patterning of organic film by wet-etching, it is desired that dry-etching is conducted to remove the remaining resin that may cause a failure in contact. Due to these, the number of processes is increased. Thus, there are problems in working property and productivity.
To prevent the increase in the number of processes to enhance the productivity, it might be suitable that the processes are conducted in the lump as much as possible. For example, after forming the SiN layer and organic film and then wet-etching the organic film, dry-etching of base layer can be conducted using the obtained organic film pattern as a mask. However, the positive type photosensitive acrylic resin lacks in resistance to dry-etching, and therefore its surface is significantly worn out by dry-etching. Therefore, such a method cannot be applied.
Also, there is the problem that the near i-line optical transmissivity of positive type photosensitive acrylic resin is low. Also, the thermal resistance of photosensitive group is not sufficient and the transmissivity is therefore like to further reduce due to the thermal treatment such as annealing in post-process. Therefore, the performance of TFT(thin-film transistor) substrate is deteriorated.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a method for efficiently producing interlayer insulating film with high transmissivity and high thermal resistance in TFT substrate with a structure where pixel electrode and wiring are overlapped.
It is a further object of the invention to provide an active matrix liquid-crystal display device including such a TFT substrate.
According to the invention, a method for making an active matrix liquid-crystal display device, comprises the steps of:
forming interlayer insulating film, at least part of which composed of organic film, on a TFT(thin-film transistor) substrate with a structure where a pixel electrode and wiring are overlapped;
patterning the organic film; and
patterning a base layer using the patterned organic film as a mask.
According to another aspect of the invention, an active matrix liquid-crystal display device, comprises:
a TFT(thin-film transistor) substrate with a structure where a pixel electrode and wiring are overlapped; and
interlayer insulating film, at least part of which composed of organic film;
wherein the organic film has a transmissivity of greater than 90% to g-line light and the heat resistance of organic film is higher than 250° C.
REFERENCES:
patent: 5926235 (1999-07-01), Han et al.
patent: 5926242 (1999-07-01), Kataoka et al.
patent: 5963279 (1999-10-01), Taguchi
patent: 0 603 866 A1 (1994-06-01), None
patent: 0 762 184 A1 (1997-03-01), None
patent: 2 311 653 (1997-10-01), None
patent: 64-73316 (1989-03-01), None
patent: 9-244009 (1997-09-01), None
patent: 9-325330 (1997-12-01), None
patent: 10-96963 (1998-04-01), None
patent: 10-161158 (1998-06-01), None
patent: 91-10623 (1991-06-01), None
NEC Corporation
Picardat Kevin M.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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