Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
1998-11-20
2001-09-04
Pham, Long (Department: 2823)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
C257S066000
Reexamination Certificate
active
06284576
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a manufacturing method of a thin-film transistor of the field-effect type that is commonly used as a switching element for pixel electrodes of liquid crystal displays and other elements.
BACKGROUND OF THE INVENTION
FIG. 4
is a plan view showing commonly used pixels on a TFT substrate for use in liquid crystal displays that is manufactured by using thin-film transistors of the field-effect type.
Signal lines
21
and gate lines
22
are installed on an insulating substrate so as to orthogonally intersect each other, and a thin-film transistor
20
having a source electrode
20
a
, a drain electrode
20
b
and a gate electrode
20
c
is placed in the vicinity of each of the intersections of the signal lines
21
and the gate lines
22
. The source electrode
20
a
is connected to the corresponding signal line
21
, the gate electrode
20
c
is connected to the corresponding gate line
22
, and the drain electrode
20
b
is connected to the corresponding pixel electrode
23
. Here, in
FIG. 4
, the reference numeral
24
represents a pixel storage capacitance.
The thin-film transistor
20
is a thin-film transistor of the so-called reversed stagger type wherein the gate electrode is placed right above the insulating substrate. Referring to FIGS.
5
(
a
) and
5
(
b
), an explanation will be given of a manufacturing method of a conventional thin-film transistor of the reversed stagger type. Here, FIG.
5
(
a
) is a plan view of a thin-film transistor of the reversed stagger type that was manufactured in a conventional method, and FIG.
5
(
b
) is a cross-sectional view taken along line B-B′ of FIG.
5
(
a
).
First, a gate-electrode material layer is formed on an electrically insulating substrate
32
, and the gate-electrode material layer is patterned into a predetermined shape by a photolithography technique consisting of coating of photoresist, a patterning process of the resist (consisting of an exposing process and a rinsing process), an etching process, a removing process of the resist, etc.; thus, gate electrodes
33
are formed. Next, the surfaces of the gate electrodes
33
are subjected to anodic oxidation so that a gate insulating film
34
is formed, and then a gate insulating film
35
is formed in a manner so as to cover the gate electrodes
33
. Additionally, the gate insulating films
34
and
35
are omitted from FIG.
5
(
a
).
Next, a semiconductor-material layer that subsequently serves as a semiconductor layer
36
and a contact-material layer
37
that subsequently serves as contact layers
37
a
and
37
b
are formed in this order, and the semiconductor-material layer and the contact-material layer
37
are patterned at the same time by the photolithography technique. In this case, since only the semiconductor layer
36
is first patterned, the pattern of a gap section
40
between the source electrode
38
and the drain electrode
39
has not yet been formed. Successively, the pattern of the gap section
40
is formed in the contact-material layer
37
by the photolithography technique so that the contact layers
37
a
and
37
b
are formed (in FIG.
5
(
a
), the contact layers
37
a
and
37
b
are indicated by cross-hatched regions). Here, there is a generally known manufacturing process in which at this time, an etching stopper layer is provided in the region of the gap section
40
between the semiconductor-material layer and the contact-material layer
37
.
Thereafter, an electrode material that subsequently serves as a source electrode
38
and a drain electrode
39
is formed, and this electrode material is patterned by the photolithography technique so that source electrode
38
and the train electrode
39
are formed. The thin-film transistor of the reversed stagger type is manufactured by the processes as described above.
In this manner, the above-mentioned manufacturing method inevitably needs to use a specific resist pattern in order to form the gap section
40
during a patterning process of the gap section
40
. This is also required in other conventional manufacturing methods similar to the above-mentioned manufacturing method.
In the current manufacturing processes of thin-film transistors, reduction of the number of processes has been a major problem to be solved in order to reduce the production costs and to improve the yield of desired products. However, in the above-mentioned conventional manufacturing methods, the production of the resist pattern used for the formation of the gap section further requires photolithography processes such as coating of resist and patterning of the resist (an exposing process and a rinsing process), resulting in a further problem of numerous processes.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide a manufacturing method of a thin-film transistor that can reduce the production costs and improve the yield of desired products by reducing the number of processes.
In order to achieve the above-mentioned objective, a manufacturing method of thin-film transistors of the present invention has the following steps: a first step of forming a gate electrode on an electrically insulating substrate; a second step of forming a gate insulating film and a semiconductor layer on the gate electrode; a third step of forming a single contact-material layer on the semiconductor layer; a fourth step of forming an electrode-material layer by forming a conductive electrode material on the contact-material layer, as well as forming a source electrode and a drain electrode by patterning the electrode-material layer; and a fifth step of patterning a gap section that divides the contact-material layer into the source-electrode side and the drain-electrode side by a dry etching with etching gases including HCl and SF
6
using the source electrode and the drain electrode as masks so that a plurality of conductive contact layers are formed, in order to obtain a construction wherein the source electrode is connected to one side of the contact layer and the drain electrode is connected to the other side of the contact layer.
In the above-mentioned manufacturing method, the gap section is patterned in the contact-material layer by carrying out the etching process using the preliminarily formed source electrode and drain electrode as masks and patterning the gap section by a dry etching with etching gases including HCl and SF
6
; therefore, the etching process can be carried out with a greater selectivity. Consequently, it is not necessary to make a resist pattern in order to etch the gap section. Consequently, since the photolithography process is eliminated, it is possible to reduce the production costs. Moreover, since the elimination of the photolithography process reduces the formation of unwanted patterns, thereby making it possible to improve the yield of desired products. Furthermore, it is possible to suppress film wear of the electrodes serving as the masks, and also to reduce an increase in resistance and generation of new products.
In order to achieve the above-mentioned objective, another manufacturing method of thin-film transistors of the present invention has the following steps: a first step of forming a gate electrode on an electrically insulating substrate; a second step of forming a gate insulating film and a semiconductor layer on the gate electrode; a third step of forming a single contact-material layer on the semiconductor layer; a fourth step of forming an electrode-material layer by forming a conductive electrode material on the contact-material layer, as well as forming a source electrode and a drain electrode by patterning the electrode-material layer; and a fifth step of patterning a gap section that divides the contact-material layer into the source-electrode side and the drain-electrode side by a dry etching with etching gases including HCl and CF
4
using the source electrode and the drain electrode as masks or using the photoresist pattern that has been used for patterning the source electrode and the drain electrode
Ban Atsushi
Okamoto Masaya
Suzuki Hisataka
Coleman William David
Pham Long
Sharp Kabushiki Kaisha
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