U.S. patent application number 09/903495 was filed with the patent office on 2002-02-07 for wiring substrate and gas discharge display device.
Invention is credited to Fukushima, Makoto, Ijuin, Masahito, Kawai, Michifumi, Murase, Tomohiko, Nishiki, Masashi, Satoh, Ryohei, Suzuki, Shigeaki, Taniguchi, Yuzo, Yabushita, Akira.
Application Number | 20020014841 09/903495 |
Document ID | / |
Family ID | 17491123 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020014841 |
Kind Code |
A1 |
Nishiki, Masashi ; et
al. |
February 7, 2002 |
Wiring substrate and gas discharge display device
Abstract
A gas discharge display device comprising a front side substrate
having a plurality of first electrodes and a back side substrate
having a plurality of second electrodes, wherein at least said
first electrodes or second electrodes are formed by wet etching
using a resist made of an inorganic material, is excellent in the
ability to suppress the breakage of wiring in electrodes.
Inventors: |
Nishiki, Masashi;
(Yokohama-shi, JP) ; Satoh, Ryohei; (Yokohama-shi,
JP) ; Taniguchi, Yuzo; (Kodaira-shi, JP) ;
Suzuki, Shigeaki; (Fujisawa-shi, JP) ; Kawai,
Michifumi; (Tokyo, JP) ; Ijuin, Masahito;
(Fujisawa-shi, JP) ; Yabushita, Akira;
(Yokohama-shi, JP) ; Fukushima, Makoto;
(Yokohama-shi, JP) ; Murase, Tomohiko;
(Kawasaki-shi, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
17491123 |
Appl. No.: |
09/903495 |
Filed: |
July 13, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09903495 |
Jul 13, 2001 |
|
|
|
09164272 |
Oct 1, 1998 |
|
|
|
6261144 |
|
|
|
|
Current U.S.
Class: |
313/587 |
Current CPC
Class: |
H01J 11/12 20130101;
H05K 3/04 20130101; H05K 3/388 20130101; H01J 11/22 20130101; H05K
2201/0175 20130101; H05K 2201/0326 20130101; H05K 2203/025
20130101; H01J 9/02 20130101; H01J 2211/225 20130101; H05K 3/062
20130101; H01J 11/24 20130101; H05K 2203/107 20130101 |
Class at
Publication: |
313/587 |
International
Class: |
H01J 017/49 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 3, 1997 |
JP |
09-270795 |
Claims
What is claimed is:
1. A gas discharge display device comprising a front side substrate
having a plurality of first electrodes and a back side substrate
having a plurality of second electrodes, at least said first
electrodes or said second electrodes being formed from a resist
made of an inorganic material by a wet etching process.
2. A gas discharge display device according to claim 1, wherein
said resist is formed by means of blaster.
3. A gas discharge display device according to claim 1, wherein
said resist is formed by means of laser.
4. A gas discharge display device according to claim 1, wherein at
least said first electrodes or second electrodes are Cr/Cu/Cr
layers and said resist and the uppermost Cr layer of said first
electrodes or second electrodes are formed by means of blaster or
laser.
5. A gas discharge display device according to claim 1, wherein at
least said first electrodes or second electrodes are Cr/Cu/Cr
layers and at least the Cr layers of said first electrodes or
second electrodes are formed by wet etching using an alkaline
etching solution.
6. A gas discharge display device according to any of claims 1 to
5, wherein said resist is an inorganic material having at least two
layers.
7. A gas discharge display device according to any of claims 1 to
6, wherein said resist is an ITO film or SiO.sub.2, or Ni--Cr.
8. A gas discharge display device comprising: a front side
substrate having a plurality of first electrodes and a first
dielectric layer covering said first electrodes, a back side
substrate having a plurality of second electrodes and a second
dielectric layer covering said second electrodes, and an inorganic
material layer interposed at least between said first electrodes
and said first dielectric layer or between said second electrode
and said second dielectric layer, said first electrodes or said
second electrodes being formed by wet etching using said inorganic
material layer.
9. A gas discharge display device according to claim 8, wherein
said inorganic material layer is formed by means of blaster.
10. A gas discharge display device according to claim 8, wherein
said inorganic material layer is formed by means of laser.
11. A gas discharge display device according to claim 8, wherein at
least said first electrodes or said second electrodes are Cr/Cu/Cr
layers and the uppermost Cr layers of said first electrodes or said
second electrodes are formed by means of blaster or laser.
12. A gas discharge display device according to claim 8, wherein at
least said first electrodes or said second electrodes are Cr/Cu/Cr
layers and at least the Cr layers of said first electrodes or said
second electrodes are formed by wet etching using an alkaline
etching solution.
13. A gas discharge display device according to any of claims 8 to
12, wherein said inorganic material layer has at least two
layers.
14. A gas discharge display device according to any of claims 8 to
13, wherein said inorganic material layer is an ITO layer or
SiO.sub.2 or Ni--Cr.
15. A gas discharge display device according to any of claims 8 to
14, wherein at least an insulating material layer is interposed
between said inorganic material layer and said dielectric
layer.
16. A gas discharge display device comprising: a front side
substrate having a plurality of first electrodes, a back side
substrate having a plurality of second electrodes, and a material
layer formed by means of blaster on at least said first electrodes
or said second electrodes, said first electrodes or said second
electrodes being formed from said material layer by wet
etching.
17. A gas discharge display device comprising: a front side
substrate having a plurality of first electrodes, a back side
substrate having a plurality of second electrodes, and a material
layer formed by means of laser on at least said first electrodes or
said second electrodes, said first electrodes or said second
electrodes being formed from said material layer by wet
etching.
18. A wiring substrate comprising a wiring pattern formed by the
use of a resist made of an inorganic material.
19. A wiring substrate comprising a wiring pattern formed by the
use of a resist formed by means of blaster.
20. A wiring substrate comprising a wiring pattern formed by the
use of a resist formed by means of laser.
21. A gas discharge display device comprising: a front side
substrate having a plurality of transparent electrodes and bus
electrodes formed on said transparent electrodes, and a back side
substrate having a plurality of address electrodes, at least said
bus electrodes or said address electrodes being made into
Cr/Cu/Cr/ITO layers, Cr/Cu/Cr/SiO.sub.2 layers,
Cr/Cu/Cr/ITO/SiO.sub.2 layers, or Cr/Cu/Cr/Ni--Cr layers.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a wiring substrate comprising a
wiring substrate with a wiring pattern formed thereon, and a gas
discharge display device using the same.
[0002] Gas discharge display devices such as plasma display and the
like make display through a self-luminescence, and therefore are
characterized in that the field angle is large, the display is easy
to see, the thickness can be lessened, and a large picture plane
can be realized. Thus, such gas discharge display devices have
become applied to display devices of information terminal
equipments and high-quality picture tubes of television. Plasma
displays are roughly classified into direct current driving type
and alternate current driving type. Among them, the alternate
current type of plasma display shows a high luminance owing to the
memory action of dielectric layer covering electrodes, and its
lifetime has reached a practical level through formation of
protective layer. This results in practical application of plasma
displays to video monitors for many uses.
[0003] FIG. 9 is a perspective view illustrating the structure of a
practical plasma display panel, wherein the front side substrate
100 is shown apart from the back side substrate 200 for the purpose
of facilitating understanding.
[0004] The front side substrate 100 comprises a display electrode
600 made of a transparent conductive material such as ITO (indium
tin oxide), tin oxide (SnO.sub.2) or the like, a bus electrode 700
made of a low-resistance material, a dielectric layer 800 made of a
transparent insulating material and a protecting layer 900 made of
magnesium oxide (MgO) or the like, all being formed on a front side
glass substrate 400.
[0005] The back side substrate 200 comprises an address electrode
1000, a barrier rib 1100 and a fluorescent material layer 1200, all
formed on a back side glass substrate 500. Although not shown in
FIG. 9, a dielectric layer 1300 is formed on the address electrode
1000, too.
[0006] By affixing the front side substrate 100 to the back side
substrate 200 so that the display electrode 600 makes an
approximately right angle with the address electrode 1000, a
discharge space region 300 is formed between the front side
substrate 100 and the back glass side substrate 500.
[0007] In this gas discharge display device, an alternate current
voltage is applied between one pair of display electrodes 600
provided on the front side substrate 100, and a voltage is applied
between the address electrode 1000 provided on the back side
substrate 200 and the display electrode 600, whereby an address
discharge is made to occur and a main discharge is generated in a
prescribed discharging cell. The main discharge generates an
ultraviolet ray, which induces emission of lights from the red-,
green- and blue-color fluorescent materials 1200 separately coated
on respective discharging cells. A display is made by emission of
these lights.
[0008] Examples of such prior gas discharge display devices are
described in, for instance, FLAT PANEL DISPLAY 1996 (Edited by
Nikkei Microdevice, 1995), pages 208-215.
[0009] Here, the method for forming the bus electrode 700 carried
on the front side substrate 100 and the address electrode 1000
carried on the back side substrate 200 will be mentioned below in
more detail. FIG. 5, 8A-80 illustrate an exemplary process for
forming address electrode 1000 on back side glass substrate 500.
Explanation of the process for forming bus electrode 700 carried on
front side substrate 100 is omitted, because it can be formed by a
similar process.
[0010] First, a Cr/Cu/Cr layer (1000a-c) for forming address
electrode 1000 on the back side glass substrate 500 and a resist
2500 for forming the pattern of address electrode 1000 are
successively piled lamination-wise by a film-forming technique such
as sputtering, evaporation, spin coating, dry filling, etc. (Step
(a), FIG. 8A: Film forming step). Next, the resist 2500 is exposed
to light and developed so as to form a desired pattern of address
electrode 1000 (Steps (b) and (c), FIG. 8B and 8C:
Photolithographic step). Next, using an etching solution for Cr,
the Cr layer 1000a is etched to form the desired pattern (Step (d),
FIG. 8D: Etching step). Next, the exposed and developed resist 2500
is peeled off, and a resist 2500 is again formed (Steps (e) and
(f), FIGS. 8E and 8F). The above-mentioned treatments are repeated
for each of Cu layer 1000b and Cr layer 1000c (Steps (g) to (o),
FIGS. 8G-80). Thus, address electrode 1000 is formed on the back
side glass substrate 500.
[0011] The above-mentioned process using an etching solution is
generally called "wet etching". In the conventional wet etching
processes, the resist 2500 is formed from an organic material.
[0012] Further, in the conventional formation of electrodes by wet
etching, a photolithographic step for forming a resist is
indispensable.
SUMMARY OF THE INVENTION
[0013] In order to reduce the number of repetition of the
photolithographic steps, the present inventors have studied on a
technique for forming a multi-layered wiring such as those having a
structure of Cr layer 1000a/Cu layer 1000b/Cr layer 1000c, etc. by
using only the resist 2500 formed by Steps (a)-(c). This technique
may be realizable if an etching solution capable of selectively
etching Cr layer or Cu layer is used. Actually, however, it has
experimentally been revealed that Cr layers 1000a and 1000c are
quite readily side-etched and accuracy of fabrication of the
Cr/Cu/Cr layer is quite unstable, so far as an etching solution
giving no damage to alkali-developable releasable resists is used.
If a Cr layer is side-etched, the side-etched portions form gaps,
which incurs inclusion of voids and contaminants such as etching
solution. The contaminants cause corrosion and breakage of wiring
in the step of firing the dielectric. Occurrence of breakage in the
wiring means existence of wire portions not contributing to display
in a gas discharge display panel, which is a fatal problem to a
display panel. Since Cr/Cu/Cr layer constitutes a wiring of lower
resistance as compared with other electrode materials, it is quite
useful for large-sized display devices such as gas discharge
display panel and the like. But, the same problem as mentioned
above arises also in case of forming a multi-layer wiring such as
Cr/Al/Cr by the method of wet etching.
[0014] Further, if the resist is formed of an organic material, the
adhesion between resist and electrode is insufficient, which causes
corrosion by etching solution at the resist interface. It has
further been revealed that, in such a resist, extraneous materials
and air bubbles are included to cause defects in resist, due to
which corrosion and thereby caused breakage of wiring can occur.
Further, since conventional resists have been formed by a
photolithographic process, they are apt to have defects due to
extraneous matter. If electrode is formed by wet etching from a
resist including defects, the regions corresponding to the defects
are similarly etched, which causes breakage of wiring. These
problems arise not only in Cr/Cu/Cr type multi-layer wiring, but
also in case of forming a wiring of Al, Ag, Ni, Au, etc. by wet
etching.
[0015] As above, in the gas discharge display panels and wiring
substrates in which electrodes are formed by the conventional wet
etching technique, breakage of wiring has readily occurred due to
side-etching of electrode and unexpected corrosion. Further,
breakage of wiring due to defects of resist has also been apt to
occur.
[0016] It is an object of this invention to suppress the breakage
of wiring in the electrodes formed in wiring substrates and gas
discharge display panels. In particular, the object of this
invention consists in suppressing the breakage of wiring in the
case of forming electrodes by wet etching process.
[0017] In order to achieve the object mentioned above, this
invention forms a resist from an inorganic material in a wet
etching process.
[0018] Thus, this invention forms a gas discharge display device
provided with a front side substrate having a plurality of first
electrodes and a back side substrate having a plurality of second
electrodes, wherein at least the first electrodes or the second
electrodes are formed from a resist made of an inorganic material
by wet etching process.
[0019] Further, this invention forms a gas discharge display device
provided with a front side substrate having a plurality of first
electrodes and a first dielectric layer covering said first
electrodes, a back side substrate having a plurality of electrodes
and a second dielectric layer covering said second electrodes and a
layer of an inorganic material layer interposed at least between
said first electrodes and said first dielectric layer or between
said second electrodes and said second dielectric layer, wherein
said first electrodes or said second electrodes are formed by wet
etching process.
[0020] Since a resist formed in the above-mentioned manner by
forming an inorganic material into a film by sputtering or
evaporation method has an increased adhesiveness to electrodes as
compared with conventional resists made of organic material, such a
resist is prevented from the corrosion by etching solution at the
resist interface and thereby the breakage of wiring can be
suppressed.
[0021] Further, if an inorganic material is used as resist, such a
resist does not require so much consideration for etching damage as
in the use of conventional resists made of organic material, so
that an etching solution facilitating the control of etching
quantity can be used, and the breakage of wiring due to side
etching occurring in the conventional technique can be prevented by
the use of inexpensive inorganic material. That is, as the
inorganic material, ITO, SiO.sub.2, Ni--Cr and the like can be
used, for instance.
[0022] Further, since the inorganic material layer is lessened in
reactivity with electrodes and dielectric layer, the inorganic
layer may be made to remain between the electrodes and dielectric
layer instead of releasing the inorganic layer, and this makes it
possible to prevent the corrosion of electrodes and breakage of
wiring due to the reaction between electrodes and dielectric
layer.
[0023] For forming a resist by the use of an inorganic material
layer, any means such as photolithography, blaster, laser and the
like may be used.
[0024] In order to achieve the object mentioned above, this
invention forms a resist by means of blaster. Thus, the gas
discharge display device of this invention comprises a front side
substrate having a plurality of first electrodes and a back side
substrate having a plurality of second electrodes, wherein at least
said first electrodes or said second electrodes have thereon a
material layer formed by means of blaster and said first electrodes
or second electrodes are formed from said material layer by wet
etching process. In this case, the material layer serves as a
resist for the first or second electrodes.
[0025] For forming the material layer, it is necessary to form a
protecting layer functioning as a resist for said material layer.
Since this invention forms the material layer (resist) by means of
a blaster, etching solution does not permeate the interface between
the protecting layer and the material layer, which lessens the risk
of forming defects in the material layer (resist). This has made it
possible to carry out the wet etching on a material having only a
small number of defects and therefore to suppress breakage of
electrodes. In addition, fabrication of a resist by means of
blaster can be achieved in a short period of time at a low
cost.
[0026] It should be additionally noted that, if the material layer
is formed by means of laser instead of blaster, the formation of
protecting layer necessary to the blaster process is unnecessary,
due to which electrodes can be formed without photolithographic
process and therefore the electrode-forming process can naturally
be shortened to a great extent. In such an embodiment, the use of
mask for forming an electrode pattern is unnecessary. Further,
since in this case the material layer (resist) is formed without
photolithographic process, a partial removal of the material layer
by means of laser is enough for obtaining a desired pattern, which
makes it possible to decrease the number of defects in resist
extremely.
[0027] In these cases, the material layer (resist) may be made of
any of organic material and inorganic material.
[0028] Further, in the case where blaster is used, the same
fabrication as achievable by means of laser can be achieved by
throttling the nozzle.
[0029] Moreover, the same processing as in the case of using a
laser is possible even if the material layer (resist) is subjected
to mechanical cutting to obtain a desired electrode pattern.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIGS. 1A-1H are process diagrams illustrating the first
embodiment of this invention.
[0031] FIGS. 2A-2L are process diagrams illustrating the second
embodiment of this invention.
[0032] FIGS. 3A-3G are process diagrams illustrating the third
embodiment of this invention.
[0033] FIGS. 4A-4E are process diagrams illustrating the fourth
embodiment of this invention.
[0034] FIGS. 5A-5D are process diagrams illustrating the fifth
embodiment of this invention.
[0035] FIGS. 6A-6E are process diagrams illustrating the sixth
embodiment of this invention.
[0036] FIGS. 7A and 7B are sectional views illustrating the gas
discharge display device of this invention.
[0037] FIGS. 8A-80 are diagrams illustrating the conventional
process.
[0038] FIG. 9 is a sectional view illustrating a conventional gas
discharge display device.
[0039] FIGS. 10A to 10D are process diagrams illustrating the
seventh embodiment of the present invention.
[0040] FIGS. 11A to 11D are process diagrams illustrating the
eighth embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0041] Embodiments of this invention will be explained below by
referring to the accompanying drawings.
[0042] FIGS. 1A-1H illustrate the first embodiment in which address
electrodes are formed on a back side substrate.
[0043] In these drawings, 10 is a back side glass substrate, and
11a, 11b and 11c are address electrodes in which Cr/Cu/Cr layers
are successively laminated. 25 is an inorganic material layer
functioning as a resist, and 26 is a photoresist layer for forming
a pattern of resist 25.
[0044] First, Cr layer 11c, Cu layer 11b, Cr layer 11a and ITO
layer functioning as an inorganic material layer 25 are
successively laminated by sputtering, and then a dry film resist
functioning as photoresist 26 is laminated (Step (a), FIG. 1A).
[0045] Subsequently, the photoresist 26 (dry film resist) is
exposed to light and developed so as to give a desired electrode
pattern, and then baked (Step (b), FIG. 1B).
[0046] Subsequently, a blast treatment using calcium carbonate is
carried out to remove the inorganic material layer 25 (ITO layer)
(Steps (c) and (d), FIGS. 1C, 1D). This fabrication of resist by
blast treatment makes it possible to form a pattern having an
approximately same width as that of resist with a very high
accuracy in a very short period of time.
[0047] Subsequently, the photoresist 26 (dry film resist) is peeled
off (Step (e), FIG. 1E). It is preferable at this time to wash away
the dusts of inorganic material layer (ITO layer) formed upon the
above-mentioned blast treatment.
[0048] Subsequently, Cr layer 11a is etched with an aqueous
solution containing potassium permanganate and sodium metasilicate
(Step (f), Fig. 1F). In this case, the above-mentioned inorganic
material layer 25 (ITO layer) acts as a resist for Cr layer 11a.
The aqueous solution containing potassium permanganate and sodium
metasilicate is an alkaline aqueous solution which can etch the Cr
layer 11a, while it scarcely etches the inorganic material layer 25
(ITO layer) and the Cu layer 11b. Thus, the inorganic material
layer 25 (ITO layer) is not substantially corroded by the alkaline
aqueous solution, and the Cr layer 11a hardly undergoes
side-etching throughout the formation. Further, since the
adhesiveness between inorganic material layer 25 (ITO layer) and Cr
layer 11a is good, the surface of Cr layer 11a in contact with
inorganic material layer 25 (ITO layer) is not corroded.
[0049] Subsequently, Cu layer 11b is etched with an aqueous
solution containing ferric sulfate and sulfuric acid (Step (g),
FIG. 1G). In this case, the inorganic material layer 25 (ITO layer)
and the Cr layer 11a act as a resist for Cu layer 11b. The aqueous
solution containing ferric sulfate and sulfuric acid is an acidic
aqueous solution which can etch the Cu layer 11b, while it hardly
etches the inorganic material layer 25 (ITO layer) and the Cr layer
11a. Thus, Cr layer 11a and Cu layer 11b are scarcely side-etched
throughout the formation.
[0050] Subsequently, Cr is again etched with an aqueous solution
containing potassium permanganate and sodium metasilicate to form
an electrode wiring having a constitution of Cr/Cu/Cr/ITO (Step
(h), FIG. 1H).
[0051] By the process mentioned above, there can be obtained an
electrode wiring having a constitution of Cr/Cu/Cr/ITO and
including suppressed breakage.
[0052] As above, by using inorganic material layer 25 (ITO layer)
as a resist, a sufficient adhesiveness can be ensured between
inorganic material layer 25 (ITO layer) and Cr layer 11a, and the
corrosion of electrodes and breakage of wiring caused by etching
solution at the resist interface can be suppressed. Further, the
resist defects of inorganic material layer 25 caused by inclusion
of extraneous matter and air bubbles can be lessened, and the
corrosion of electrodes and breakage of wiring caused by etching
solution can be suppressed.
[0053] Further, the use of inorganic material layer 25 as a resist
broadens the scope of selection of etching solution, and the
side-etching of Cr layers 11a and 11c in the conventional technique
can be suppressed. Further, consideration of the etching damage to
resist has become unnecessary.
[0054] Further, the use of blaster such as sandblast and the like
in place of conventional etching solutions makes it possible to
suppress the resist defects in inorganic material layer 25. That
is, since there is no permeation of etching solution through the
interface between photoresist 26 and inorganic material layer, the
possibility of forming defects in inorganic material layer 25
(resist) is not great. By carrying out a wet etching process using
such a inorganic material layer 25 (resist) small in the number of
defects, the breakage of electrodes can be suppressed.
[0055] Further, in this electrode-forming process, Cr layer is
etched with an alkaline aqueous solution. In the conventional
technique for forming alkali-resistant organic resist by
photolithographic process, the developing solution and peeling
solution for the organic resist have been expensive and have caused
environmental pollution. On the other hand, in the process of this
invention employing an inorganic resist, the resist is lessened in
reactivity with electrodes and dielectric, and therefore a step for
peeling off the resist is unnecessary and no peeling solution is
needed. Further, since inorganic resist is formed by means of
blaster in place of photolithographic process, the use of developer
for alkali-resistant organic resist is also unnecessary. In other
words, there is no problem concerning developing solution and
peeling solution for organic resist, unlike in the conventional
techniques.
[0056] Next, FIGS. 2A-2L illustrate the second embodiment for
forming address electrodes on a back side substrate.
[0057] In the embodiment of FIG. 1, it has been revealed that a
small quantity of etching solution for Cu layer can remain in the
defective portions such as pin-holes of inorganic material layer 25
(ITO layer) in the etching process of Cu layer 11b to corrode Cu
layer in the subsequent steps. Accordingly, in FIG. 2, electrodes
are formed by the following processes.
[0058] First, by the same processes as in FIG. 1, Cr layer 11a is
etched (Steps (a)-(f), FIGS. 2A-2F).
[0059] Subsequently, photoresist 26 (dry film resist) not corroded
by an etching solution for Cu is laminated on an inorganic material
layer 25 (ITO layer) (Step (g), FIG. 2G) and then exposed to light
so as to make a pattern covering the inorganic material layer 25
(ITO layer) and developed (Step (h), FIG. 2H). Then, the unexposed
portion of photoresist 26 (dry film resist) is removed (Step (i),
FIG. 2I), and the Cu layer 11b is etched with the same etching
solution as in FIG. 1 (Step (j), FIG. 2J). Thereafter, the
photoresist 26 (dry film resist) is peeled off (Step(k), FIG. 2K).
The subsequent processes are carried out in the same manner as in
FIG. 1.
[0060] By the above-mentioned treatment, the etching solution for
Cu becomes unable to remain in the defects, such as pin-holes, in
the inorganic material layer 25 (ITO layer), by which the corrosion
of Cu layer in the subsequent steps can be suppressed.
[0061] Next, FIGS. 3A-3G illustrate the third embodiment in which
address electrodes are formed on the back side substrate.
[0062] This embodiment is the same as that of FIG. 1, except that
the blast treatment using calcium carbonate is carried out not only
on the inorganic material layer 25 (ITO layer) but also on the Cr
layer 11a (Step (d), FIG. 3D), and after etching the Cu layer 11b
(Step (e), FIG. 3E) the photoresist 26 (dry film resist) is peeled
off (Step (f), FIG. 3F). Accordingly, the photoresist 26 (dry film
resist) is selected from materials not etched by the etching
solution for Cu layer 11b.
[0063] In the above-mentioned treatment, the step for etching Cr
layer 11a can be eliminated, and the electrode-forming process can
be simplified. Further, if the efficiencies of blast process and
wet etching process are taken into consideration, it is preferable
to fabricate down to the Cr layer 11a by blast process because of
the material characteristics of Cu layer 11b and film thickness
thereof. As above, an electrode formation by combination of a dry
etching method such as blast process and a wet etching method is
effective for simplification of process and prevention of breakage
of wiring.
[0064] Next, FIGS. 4A-4E illustrate the fourth embodiment in which
address electrodes are formed on a back side substrate.
[0065] FIG. 4 is an example of forming electrodes without using
photolithographic process.
[0066] First, Cr layer 11c, Cu layer 11b, Cr layer 11a and ITO
layer functioning as an inorganic material layer 25 are
successively formed on a glass substrate 10 by sputtering (Step
(a), FIG. 4A).
[0067] Subsequently, the inorganic material layer 25 (ITO layer) is
removed by means of laser so as to give a desired electrode pattern
(Step (b), FIG. 4B).
[0068] Thereafter, Cr layer 11a, Cu layer 11b and Cr layer 11c are
successively etched in the same manner as in FIG. 1 to form an
electrode wiring (Steps (c)-(e), FIGS. 4C-4E).
[0069] As above, a resist can be formed by using a laser, without
such photolithographic steps as shown in FIGS. 1-3, by which the
electrode-forming process can be simplified greatly. Further, the
mask for forming electrodes becomes unnecessary.
[0070] Since there is no photolithographic process, the resist
defects due to unexposed portions caused by adhesion of extraneous
matter can be eliminated, so that the breakage of wiring at the
time of wet etching caused by the resist defects can be suppressed.
That is to say, an electrode-forming process resistant to
extraneous matter can be realized.
[0071] It is also possible to subject the layers of down to Cr 11a
to laser fabrication, if desired, as shown in FIG. 3. This method
is realizable as understandable from thickness of Cr layer, and an
experiment has actually proved that a fabrication of high accuracy
can be achieved by this method. The process is as shown in FIGS.
5A-5D.
[0072] It has been revealed that , in the processes of FIGS. 4 and
5, a very small quantity of etching solution for Cu layer 11b can
remain in the defective portions such as pin-holes of inorganic
material layer 25 (ITO layer) in the etching process of Cu layer
11b and this remaining etching solution corrodes the Cu layer in
the subsequent steps. In order to solve this problem, in the
embodiment shown by FIGS. 6A-6E, electrodes are formed by the
following process. FIG. 6 is explained by imagining the process of
FIG. 5.
[0073] First, Cr layer 11c, Cu layer 11b and Cr layer 11a are
successively formed on glass substrate 10 by sputtering, after
which thereon are formed an ITO layer functioning as inorganic
material layer 25 and a resist 27 not corroded by the etching
solution for Cu layer 11b (Step (a), FIG. 6A).
[0074] Subsequently, resist 27, inorganic material layer 25 and Cr
layer 11a are removed by means of laser so as to give a desired
electrode pattern (Step (b), FIG. 6B). Since resist 27 is formed by
means of laser as above, there is no need to use such a
photosensitive material as used in conventional photolithographic
process as a material of resist 27.
[0075] Subsequently, Cu layer 11b is etched in the presence of
resist 27 by the use of an aqueous solution containing ferric
sulfate and sulfuric acid (Step (c), FIG. 6C). Since the inorganic
material layer 25 is covered with resist 27, the inorganic material
layer 25 is not readily corroded.
[0076] Then, the resist 27 is peeled off, and the Cr layer 11c is
etched with an aqueous solution containing potassium permanganate
and sodium metasilicate (Step (d), FIG. 6D). If desired, the resist
27 may be peeled off after Step (e).
[0077] By the above-mentioned process, an electrode wiring having a
constitution of Cr/Cu/Cr/ITO and lessened in the risk of wiring
breakage caused by side-etching can be obtained (Step (e), FIG.
6E).
[0078] After this treatment, no etching solution for Cu remains in
the inorganic material layer 25 (ITO layer), and corrosion of Cu
layer in the subsequent steps can be suppressed.
[0079] Next, there is explained an electrode with lower cost by
reducing side etching and reducing the number of steps comparing
with the above-mentioned embodiments.
[0080] FIGS. 10A to 10D show the seventh embodiment of the present
invention wherein the electrode is formed by reducing the number of
film formation by sputtering, etc. and aiming at a lower production
cost.
[0081] First, Cr layer 11c, Cu layer 11b and an alloy layer of Ni
and Cr as an inorganic material layer 25 are formed on a glass
substrate 10 by sputtering (Step (a), FIG. 10A). Since the alloy
layer of Ni and Cr is used, selective etching of the Cr layer 11c
and Cu layer 11b becomes possible in a later step. Further, the
alloy layer of Ni and Cr can easily be subjected to laser
processing.
[0082] Then, the inorganic material layer 25 (the alloy layer of Ni
and Cr) is removed by using a laser so as to give a desired
electrode pattern (Step (b), FIG. 10B). Needless to say, it is
possible to employ the above-mentioned blast treatment.
[0083] Subsequently, the Cu layer 11b and the Cr layer 11c are
etched in this order in the same manner as shown in FIG. 3 to form
an electrode wiring (Steps (c) and (d), FIGS. 10C and 10D).
[0084] This electrode construction does not require the Cr layer
11a mentioned in the above-mentioned embodiments, and thus can omit
the film forming step of the Cr layer 11a, resulting in making it
possible to further reduce the production cost. Further, the
electrode comprising the Cr layer 11c, the Cu layer 11b and the
Ni--Cr alloy layer is effective for preventing wire breaking caused
by side etching, as well as for increasing the adhesiveness between
the Cr layer 11c and the substrate 10, making the resistance lower
by the Cu layer 11b, and preventing the reaction with a dielectric
layer (not shown in the drawing) by the Ni--Cr alloy layer, so that
requirements demanded for a plasma display panel can be satisfied.
It is possible to use SiO.sub.2, ITO Si, Ni, etc. in place of the
Ni--Cr alloy layer.
[0085] FIGS. 11A to 11D show eighth embodiment of the present
invention wherein the electrode is formed by reducing the number of
film formation by sputtering, etc. and using a thickened Cr layer
as the inorganic material layer 25.
[0086] First, a Cr layer 11c, a Cu layer 11b and a thick Cr layer
which is to become an inorganic material layer 25 are formed in
this order by sputtering on a glass substrate 10 (Step (a), FIG.
11A). The thickness of the Cr layer 25 is preferably 3 times or
more compared with the thickness of the Cr layer 11c, in order to
set the process conditions mentioned below easier.
[0087] Then, the thick Cr layer (used as an inorganic material
layer 25) is removed using a laser to give a desired electrode
pattern (Step (b), FIG. 11B). Needless to say, the blast processing
can be used as mentioned in the above-mentioned embodiments.
[0088] Subsequently, the Cu layer 11b and the Cr layer 11c are
etched in this order in the same manner as shown in FIG. 3 to form
an electrode wiring (steps (c) and (d), FIGS. 11C and 11D).
[0089] In this case, when the Cr layer 11c is etched, the thick Cr
layer (inorganic material layer 25) is also etched to reduce the
thickness, but by making the thickness of the thick Cr layer
(inorganic material layer 25) sufficiently larger than that of the
Cr layer 11c, it is possible to form an electrode having no problem
in reliability. Further, by making the thickness of the thick Cr
layer larger, pin holes are hardly formed in the thick Cr layer,
resulting in reducing the residual amount of an etching solution
for the surface of the Cu layer 11b. This makes it possible to
prevent corrosion of the Cu layer in later steps due to the
remaining etching solution.
[0090] By making the thickness of the Cr layer 25 larger, even if
there is no selectivity for etching of the underlayer Cu layer 11b
and the Cr layer 11c, the electrode can be formed by a combination
of dry etching such as a conventional layer processing and wet
etching.
[0091] Next, one example of the gas discharge display panel formed
by the above-mentioned electrode-forming processes will be
explained by referring to FIG. 7.
[0092] FIGS. 7A and 7B illustrate a gas discharge display panel,
provided that FIG. 7A is a sectional view parallel to address
electrodes and FIG. 7B is a sectional view perpendicular to the
address electrodes. The above-mentioned electrode-forming processes
are applied to both of front side substrate and back side
substrate.
[0093] In these drawings, 10 is a back side glass substrate, 11 is
an address electrode, 12 is a thin film dielectric layer such as
SiO.sub.2, 13 is a thick film dielectric layer, 14 is a front side
glass substrate, 15 is a transparent electrode such as ITO, 16 is a
bus electrode such as Cr--Cu--Cr, 17 is a thin film dielectric
layer such as SiO.sub.2, 18 is a thick film dielectric layer, 19 is
a protecting film made of, for example, MgO, 20 is a sealing
member, 21 is an electrode connected from the external circuit, 22
is an anisotropic conductive sheet containing conductive particles,
23 is a partition wall, 24 is a fluorescent material layer, and 25
is an inorganic material layer functioning as a resist at the time
of electrode formation.
[0094] A front side substrate can be formed in the following
manner.
[0095] First, a transparent electrode 15 is formed on a glass
substrate 14. The transparent electrode 15 may be formed by any
means of wet etching, blaster and laser. The use of laser is
preferred from the viewpoint of simplification of the process.
Subsequently, a bus electrode 14 is formed on the transparent
electrode 15 according to the above-mentioned electrode-forming
process of this invention. At this time, the above-mentioned
inorganic material layer 25 exists on the bus electrode 16.
Subsequently, a thin film dielectric layer 17 is formed so as to
cover at least the transparent electrode 15 and the bus electrode
16. For instance, the thin film dielectric layer 17 is formed on
the whole panel surface. Subsequently, a thick film dielectric
layer 18 is formed on the thin film dielectric layer 17 by the
thick film printing technique. Subsequently, a protecting film 19
made of MgO or the like is formed on the thick film dielectric
layer 18 by the technique of evaporation. In the case of front side
substrate, the transparent electrode 15 is formed under the bus
electrode 16, and the transparent electrode 15 is usually an ITO
layer. Accordingly, it is allowable, if desired, to form the bus
electrode 16 including the transparent electrode 15 and the
inorganic material layer 25 according to a series of wet etching
processes by applying the electrode-forming process of this
invention. In this case, ITO/Cr/Cu/Cr/ITO are successively formed,
and then Cr/Cu/Cr/ITO functioning as bus electrode 16 is formed by
any of the above-mentioned electrode-forming processes of this
invention. Subsequently, a resist capable of making the ITO layer,
functioning as transparent electrode 15, into a desired pattern is
formed, and the ITO layer is etched by the use of this resist and
then the resist is peeled off to form a transparent electrode 15
and a bus electrode 16. The inorganic material layer 25 may be made
of SiO.sub.2 or Ni--Cr, if desired.
[0096] On the other hand, a back side substrate is formed in the
following manner.
[0097] First, an address electrode 11 is formed on a glass
substrate 10 according to the electrode-forming process of this
invention. Subsequently, a thin film dielectric layer 12 is formed
so as to cover at least the address electrode 11. For instance, the
thin film dielectric layer 12 is formed on the whole panel surface.
Subsequently, a thick film dielectric layer 13 is formed on the
thin film dielectric layer 12 according to the thick film printing
technique. Subsequently, on the thick film dielectric layer 13, a
partition wall 23 is formed and further a fluorescent material
layer 24 is formed thereon by the printing technique. The partition
wall 24 may be formed as stripes parallel to the address electrode
or as grids surrounding the display cell.
[0098] After adjusting the positions of the front side substrate
and the back side substrate formed above, they are sealed by means
of a sealing member 21. The atmosphere of the sealed space contains
a rare gas. The electrode 21 leading to the external circuit is
connected via an external connection terminal of the front side
substrate and an anisotropic conductive sheet of the back side
substrate, in order to simplify the connecting process.
[0099] As above, the inorganic material layer 25 is free from the
risk of reaction with address electrode 11, dielectric layer 18,
bus electrode 16 and dielectric layer 13, and therefore the
inorganic material layer can be left to remain without peeling.
This makes it possible to suppress the reactions between address
electrode 11 and dielectric layer 18 and between the bus electrode
16 and the dielectric layer 13, and thereby to prevent the
corrosion of address electrode 11 and bus electrode 16.
Accordingly, there arises no problem, if the thin film dielectric
layer 12 is not formed.
[0100] As above, as a result of forming the bus electrode and
address electrode as a Cr/Cu/Cr/ITO layer or a Cr/Cu/Cr/SiO.sub.2
layer, or a Cr/Cu/Cr/Ni--Cr layer, the breakage of wiring due to
various causes can be lessened.
[0101] For further lessening the breakage of wiring, a different
resist may be used in either of Cr layer 11a, Cu layer 11b and Cr
layer 11c. Another allowable means for achieving this object is to
form the inorganic material layer into a double layer structure
having a constitution of Cr/Cu/Cr/ITO/SiO.sub.2.
[0102] It is needless to say that, in the embodiments described
above, the same effect as above can be obtained if the Cr/Cu/Cr
electrode wiring is replaced by Cr/Al/Cr, Ag, Ni, Au, Al, etc. That
is to say, it is needless to say that the same effect as above can
be obtained if the materials used therein are those satisfying the
conditions required of a gas discharge display panel. It is also
needless to say that the electrode to be formed is not restricted
to the address electrode but the same effect as above can be
obtained by forming the bus electrode of the front side substrate
as shown in FIG. 7. Further, it is needless to say that this
invention can be applied not only to gas discharge display panel
but also to all the wiring substrates in which electrodes are
formed by wet etching technique.
[0103] It is also needless to say that the corrosion of electrode
at the resist interface can be prevented even if neither blaster
nor laser is used, so far as the inorganic material layer 25
(resist) is present. Conversely, it is also needless to say that
defects of resist can be suppressed even if the resist is not made
of an inorganic material, so far as the resist is formed by means
of blaster or laser.
[0104] As above, according to this invention, the breakage of wire
in the electrodes formed in wiring substrate or gas discharge
display device can be suppressed. Especially, the breakage of wire
occurring in the case of forming electrodes by wet etching
technique can be suppressed.
* * * * *