Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2002-02-25
2004-07-27
Duda, Kathleen (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S317000
Reexamination Certificate
active
06767694
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for forming a pattern of a semiconductor device used in a liquid crystal display apparatus and a method for producing a liquid crystal display apparatus using the process for forming a pattern, and in particular, to a process for forming a complicated pattern such as wiring in a simplified manner, and a method for producing a liquid crystal display apparatus using the process.
2. Description of the Prior Art
A method for producing a liquid crystal display apparatus uses a photolithography technique and a dry etching technique to produce an integrated circuit. To reduce process steps for producing the integrated circuit in the process for producing a liquid crystal display apparatus, methods for reducing the number of the total process steps for forming patterns such as wirings are exercised as well as methods to reduce the production cost thereof.
Among a variety of proposals to greatly reduce the production cost, one method proposes that two or more PR process steps required in the conventional technique can be reduced to only one process step.
That is, the first conventional example (JP-A-2000-206571) applies the above-stated method to a manufacturing process of an inversely staggered thin film transistor (hereinafter referred to as a “TFT”), and
FIGS. 1A
to
2
B are schematic cross sectional views of associated regions in a vicinity of a TFT showing main process steps of the manufacturing process.
As shown in
FIG. 1A
, a gate electrode
533
and a gate insulating film
534
are formed on a first transparent electrode
501
, and then an amorphous silicon (a-Si) film
541
, an n
+
type amorphous silicon (n
30
type a-Si) film
542
and a metal film
543
for source/drain electrodes are deposited in order thereon. A photosensitive film is further coated on the metal film
543
to a thickness of from 1 to 2 &mgr;m and then exposed and developed to form a thick photosensitive film pattern
527
having a thick film thickness and a thin photosensitive film pattern
526
having a thin film thickness.
As shown in
FIG. 1B
, the metal film
543
is etched and removed by using the thick photosensitive film pattern
527
and the thin photosensitive film pattern
526
as a mask to expose the n
+
type a-Si film
542
.
As shown in
FIG. 2A
, the n
30
type a-Si film
542
and the a-Si film
541
thereunder are subjected to dry etching step together with the thin photosensitive film pattern
526
and the metal film
543
is exposed between the thick photosensitive film patterns
527
left after the dry etching.
As shown in
FIG. 2B
, the metal film
543
and the n+ type a-Si film
542
are etched and removed by using the remaining thick photosensitive film pattern
527
as a mask. At this time, a part of the a-Si film
541
is simultaneously etched.
As described above, two different patterns of the film to be etched can be formed by utilizing the photosensitive film patterns
527
and
526
having different film thicknesses.
Also the following second conventional example (JP-A-2000-164584) applies the above-stated method to a manufacturing process of an inversely staggered TFT, and
FIGS. 3A
to
3
C are schematic cross sectional views of a region of a TFT, a gate terminal electrode and a drain terminal electrode showing the main process steps in the order of manufacturing process.
As shown in
FIG. 3A
, a gate electrode
633
, a gate terminal electrode
693
and a gate insulating film
634
are formed on a first transparent substrate
601
, and an a-Si film
641
, an n type a-Si film
642
and a metal film for source/drain electrodes are sequentially deposited thereon. The metal film and the n
+
type a-Si film
642
thereunder are then patterned to have the same pattern to form a source electrode
659
and an ohmic layer thereunder, a drain electrode
658
and an ohmic layer thereunder, and a drain terminal electrode
678
and an ohmic layer thereunder. After depositing a passivation film
640
thereon, a resist pattern is formed such that openings are formed therein above the gate terminal electrode
693
and the drain terminal electrode
678
, a thin photosensitive film pattern
626
having a thin film thickness is formed above the source electrode
659
and a separation region
660
to separate an a-Si film next thereto, and a thick photosensitive film pattern
627
having a thick film thickness is formed above the other regions.
Subsequently, as shown in
FIG. 3B
, the thin photosensitive film pattern
626
is etched and removed by utilizing the resist pattern while optimizing the etching conditions so as to at least remove the photosensitive film pattern
626
, whereby the passivation film
640
on the drain terminal electrode
678
is completely removed and the films ranging from the passivation film
640
to a part of the gate insulating film
634
in a vertical direction on the gate terminal electrode
693
are removed.
Furthermore, as shown in
FIG. 3C
, both the passivation film
640
and the a-Si film
641
corresponding to the a-Si film separation region
660
are removed and simultaneously a part of the gate insulating film
634
remaining on the gate terminal electrode
693
is removed by optimizing the etching conditions.
According to the manufacturing process of the second conventional example, the contact holes on the respective electrodes are formed and the a-Si film is separated through only one PR process step by utilizing the resist film having different film thicknesses.
Techniques employed in both the first and second conventional examples described above are developed to reduce the number of manufacturing process steps in the following manner. That is, after coating a photosensitive film of a single layer on a film to be etched, a photosensitive film pattern having different film thicknesses is formed by utilizing an exposure having different amounts of light, and the film to be etched is etched by utilizing the difference in film thickness thereof.
However, in the first and second conventional examples, when the thin photosensitive film pattern out of the photosensitive film pattern is etched and removed, the thick photosensitive film pattern is also etched to have an appearance largely different from that of the thick photosensitive film pattern before being etched since the appearance of the thick photosensitive film pattern is continuously changed in accordance with passage of time during the etching. Therefore, it is expected that by using the thick photosensitive film pattern as a mask, the film to be etched is etched to have a pattern greatly different from that designed by a process designer.
SUMMARY OF THE INVENTION
An object of the invention is to provide a process for forming a pattern and a manufacturing process for producing a liquid crystal display apparatus using the same, in which in the event a film to be etched is etched by utilizing a photosensitive film pattern (hereinafter referred to as a resist pattern) having difference film thicknesses, while a thick resist portion of the resist pattern having a film thickness thicker than that of a thin resist portion thereof is being exposed to the atmosphere used for etching and removing the thin resist portion, the shape of the thick resist pattern can be maintained.
The first aspect of the process for forming a pattern in accordance with the invention comprises:
a resist pattern formation step of coating a first resist film and a second resist film in order on a film to be etched on a substrate, and further, forming a resist pattern by patterning the first resist film and the second resist film to make the first resist film broader than the second resist film while making the second resist film positioned on the first resist film;
a first patterning step of etching the film to be etched to form a first pattern in the film to be etched by using the resist pattern as a mask; and
a resist etching step of etching the resist pattern to remove at least a portion of the first resist film
Duda Kathleen
Hayes & Soloway P.C.
NEC LCD Technologies Ltd.
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