JPH0376232A - Manufacture of display device - Google Patents

Abstract

PURPOSE:To enhance the displaying quality by a method wherein an insulating substrate is coated with a negative type sensitive polyimide as if covering a gate electrode formed on the insulating substrate; the polyimide is exposed and developed to be partly removed on the gate electrode of the sensitive polyimide; the surface is anodic- oxidized to form the first gate insulating layer for setting the sensitive polyimide. CONSTITUTION:A glass substrate 1 is coated with a negative type sensitive polyimide 10 as if covering a gate electrode 2 to irradiate another sensitive polyimide 3 with ultraviolet ray UV. Next, the sensitive polyimide 3 is ultrasonics-developed by a developer to remove the sensitive polyimide 10 on the gate electrode 2 not irradiated with the ultraviolet ray UV for drying up, heating and temporary setting processes. Next, a glass substrate 1 whose surface is covered with the sensitive polyimide 10 is immersed in an electrolyte comprising water solution, etc., containing phosphoric acid, citric acid to anodic-oxidize the surface of Ta constituting the gate electrode 2 by impressing the electrode 2 with positive voltage for the formation of the first gate insulating layer 3 comprising Ta2O5 and later the sensitive polyimide 10 is set by heat treatment. Accordingly, the surfaces of the first gate insulating layers 3 and the sensitive polyimide 10 can be flattened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a display device such as an active matrix liquid crystal display, and particularly to a method of manufacturing a thin film transistor (TPT) and an electrode bus bar constituting the display device.

[Prior Art] FIGS. 2(a) to 2(f) are process explanatory diagrams for explaining a conventional method of manufacturing a display device.

In the conventional manufacturing method, as shown in FIG.
A gate electrode 32 made of an alloy containing a is formed, and then,
As shown in FIG. 3B, the surface of the gate electrode 32 is anodized to form a first gate insulating layer 33.

Next, as shown in FIG. 3C, a second gate insulating layer 34 is formed to cover the first gate insulating layer 33, and a semiconductor active layer 35 and an ohmic contact layer 36 are formed thereon. .

Next, as shown in FIG. 3D, a source electrode 37 and a drain electrode 38 are formed on the ohmic contact layer 36.

Next, as shown in FIG. 5(e), the portion of the ohmic contact layer 36 located between the source electrode 37 and the drain electrode 38 is removed by etching, and finally, as shown in FIG. , a pixel electrode 39 made of ITO is formed on the second insulating layer 34 .

[Problem to be solved by the invention]

However, in the conventional manufacturing method described above, the second insulating layer, the semiconductor active layer,
An ohmic contact layer is formed, and then a source electrode and a drain electrode must be formed on top of it as shown in FIG. There was a problem in that the drain electrode was prone to disconnection and the manufacturing yield was poor.

In addition, in display devices such as liquid crystal displays manufactured by conventional methods, the surface has large irregularities due to the gate electrode and the first gate insulating layer, and the alignment treatment film formed on the surface also has large irregularities. However, there were problems in that rubbing defects and rubbing damage were likely to occur, and display characteristics such as contrast and viewing angle were likely to deteriorate.

In order to solve the above problem, it is possible to reduce the thickness of Ta and Ta20s that make the gate electrode and the first gate insulating layer by 1ffJe, but if Ta is made thinner, the wiring resistance of the gate electrode busbar increases. , the rise of the gate signal pulse becomes slow, and if the thickness of the Ta205 film is made thinner, it becomes impossible to obtain sufficient insulation properties, and in both cases there are problems in that the display quality deteriorates.

Therefore, the present invention has been made to solve the problems of the prior art as described above, and its purpose is to:
It is an object of the present invention to provide a method for manufacturing a display device that can improve display quality and has a high manufacturing yield.

Another object of the present invention is to provide a method for manufacturing a display device that can improve display quality, have a good manufacturing yield, and easily adjust the resistance value of a bus electrode.

[Means to solve the problem]

In the method for manufacturing a display device according to the present invention, a positive electrode is formed on the surface of a transparent insulating substrate. a step of forming a gate electrode made of a metal that can form an insulator through oxidation; a step of applying negative photosensitive polyimide onto the substrate so as to cover the gate electrode; A step of exposing the photosensitive polyimide to light, a step of developing the photosensitive polyimide and removing only the portion of the photosensitive polyimide on the gate electrode that was not exposed to light, and anodizing the surface of the gate electrode. a step of forming a first gate insulating layer; a step of curing the photosensitive polyimide by heat treatment; and a step of forming a second gate insulating layer on the cured photosensitive polyimide and the first gate insulating layer. , forming a semiconductor active layer, a source electrode, a train electrode, and a pixel electrode on the second gate insulating layer.

Further, a method for manufacturing a display device according to another invention includes forming, on the surface of a transparent insulating substrate, an electrode bus bar made of a metal in which an insulator can be formed by anodic oxidation, and a gate electrode connected to the electrode bus bar. a step of applying a negative photosensitive polyimide onto the substrate so as to cover the electrode busbar and the gate electrode; and a step of applying a photosensitive polyimide on the back side of the substrate to cover a part of the electrode busbar and the gate electrode. A step of applying a mask and applying a first exposure to the photosensitive polyimide from above the photomask, a step of applying a second exposure to the photosensitive polyimide from the back side of the substrate, and developing the photosensitive polyimide. and a step of removing the unexposed portion of the photosensitive polyimide on the electrode bus bar and the photosensitive polyimide on the gate electrode, and anodizing the portion of the electrode bus bar not covered with the photosensitive polyimide and the gate electrode. By doing so, the thickness of the electrode busbar is reduced, step 1 of forming a first gate insulating layer on the gate electrode, a step of heat-treating and curing the photosensitive polyimide, and a step of curing the photosensitive polyimide. forming a second gate insulating layer on the first gate insulating layer, a semiconductor active layer on the second gate insulating layer, and a source electrode on the second gate insulating layer; , forming a drain electrode and a pixel electrode.

[For production]

In the present invention, negative photosensitive polyimide is applied to cover the gate electrode formed on the insulating substrate, exposed to light from the back side of the substrate, and developed.
Only the portion of the photosensitive polyimide on the gate electrode is removed. Then, the surface of the gate electrode is anodized to form a first gate insulating layer, and the photosensitive polyimide is hardened by heat treatment. Therefore, the upper surfaces of the first gate insulating layer and the photosensitive polyimide are flattened, and the second gate insulating layer and the semiconductor active layer formed on the photosensitive polyimide and the first gate insulating layer can be formed flat. The height difference between the source electrode and the train electrode formed thereon becomes smaller.

In another invention, a photomask covering a part of the photosensitive polyimide electrode busbar formed on the surface of an insulating substrate and a part of the photosensitive polyimide gate electrode is applied, and a first mask is applied from above the photomask. Exposure is performed, second exposure is performed from the back side of the substrate, the photosensitive polyimide is developed, and the portion (part) of the photosensitive polyimide on the electrode busbar and the portion on the gate electrode are removed. Then, by anodizing the electrode busbar and the gate electrode, the thickness of the electrode busbar is reduced, and a first gate insulating layer is formed on the gate electrode, and the photosensitive polyimide is hardened by heat treatment. Therefore, the upper surfaces of the first gate insulating layer and the photosensitive polyimide are planarized. Therefore, the upper surfaces of the first gate insulating layer and the photosensitive polyimide are flattened, the step difference between the source electrode and the drain electrode can be reduced, and the wiring resistance of the electrode busbar can be easily set.

[Actual example]

The present invention will be explained below based on illustrated embodiments.

FIGS. 1(a) to 1(f) are process descriptions for explaining one embodiment of a method for manufacturing a display device (more specifically, TPT and a pixel electrode that constitute one pixel of a display device) according to the present invention. It is a diagram.

In the manufacturing method of this example, first, Ta is formed to a thickness of 0.2 to 0.3 μm on the surface of a glass substrate l by sputtering, and unnecessary portions of Ta are removed by photolithography and dry etching. A gate electrode 2 as shown in FIG. 3(a) is formed.

Next, as shown in FIG. 2(b), a gate voltage f! is applied on the glass substrate 1. A negative photosensitive polyimide (for example, manufactured by Toshisha Co., Ltd., trade name: Photonice) 10 is applied to a thickness of 1.0 to 2.0 μm using a spin cord so as to cover the glass. The photosensitive polyimide 3 is irradiated with ultraviolet light from the back side of the substrate 1.

Next, the photosensitive polyimide 3 is ultrasonically developed using a developer (manufactured by Toshisha Co., Ltd., product number: DV-140), and as shown in FIG. The photosensitive polyimide 10 was removed, ultrasonic rinsed with isopropanol, then dried,
Temporarily harden by heating at °C for 0.5 to 1 hour.

Next, the glass substrate 1 provided with this gate electrode 2 and whose surface was covered with photosensitive polyimide 10 was heated with phosphoric acid,
The gate electrode 2 is immersed in an electrolytic solution consisting of an aqueous solution of citric acid, oxalic acid, ammonium borate, ammonium tartrate, etc., and a positive voltage is applied to the gate electrode 2.
As shown in the figure (d), a first gate insulating layer 3 made of Ta205 with a thickness of 0.2 to 0.4 μm is formed by anodizing the surface of Ta constituting the
The photosensitive polyimide 10 is cured by heat treatment at 0° C. for 0.5 to 1.0 hours.

Next, as shown in the same figure (e), silicon nitride JIQ (S) is deposited on the glass substrate 1 by plasma CVD method using silane (StH) and ammonia (NH3) as raw material gases.
The second gate insulating layer 4 made of iN) has a thickness of 0.1 to 0.5μ.
A semiconductor active layer 5 made of amorphous silicon (a-3i) is formed to have a thickness of 0.02 m and is made of amorphous silicon (a-3i) using silane as a source gas.
Form to a thickness of ~0.5 μm. Subsequently, an ohmic contact layer 6 made of amorphous silicon (n"-a-3t) to which phosphorus is added using silane and phosphine (PH3) as raw material gases is formed to a thickness of 0.02 to 0.2 .mu.m.

Next, Cr and AJ are deposited on the ohmic contact layer 6.

The source electrode 1i made of an alloy containing Mo and Ti is
! 7 and a drain electrode 8 are formed, and a portion of the ohmic contact layer 6 located between the source electrode 7 and the drain electrode 8 is removed to form a pixel type i9 made of ITO.

FIG. 3 is a sectional view showing a case where the TPT and pixel electrode manufactured by the above method are incorporated into an active matrix liquid crystal display as a display device. In the figure, the same components as in FIG. 1 are given the same reference numerals and explained. In the liquid crystal display, a passivation W made of silicon nitride or silicon oxide is added to the structure of FIG. 3(e): ! 11 is formed, an alignment treatment film 12 is formed thereon, and alignment treatment is performed by rubbing.

On the other hand, a color filter 13, a black mask 14, and a counter electrode 15 are located at a predetermined distance from the alignment film 12.
, a glass substrate 17 provided with an alignment treatment [16,
Liquid crystal 18 is injected between two glass substrates 1 and 17.

According to the manufacturing method of this embodiment described above, the photosensitive polyimide 10 is applied so as to cover the gate electrode 2 formed on the glass substrate 1, and the portion of the photosensitive polyimide 10 on the gate electrode 2 is coated. After the removal, the first gate insulating layer 3 is formed by anodic oxidation and the photosensitive polyimide 10 is cured, so that the first gate insulating layer 3 and the photosensitive polyimide 10 are bonded together as shown in FIG. 1(d). The upper surface of 10 is flattened, and the second gate insulating layer 4 and semiconductor active layer 5 formed thereon can be formed flat. Therefore, the step difference between the source electrode 7 and the drain electrode 8 formed thereon via the ohmic contact layer 6 is much smaller than that of the conventional one shown in FIG. Disconnection of source electrode 7 and drain electrode 8 (
(also known as "step breakage") is less likely to occur.

Furthermore, since the top surfaces of the first gate insulating layer 3 and the photosensitive polyimide 10 are flattened, the unevenness of the alignment film 16 shown in FIG. 3 is reduced, making the alignment process easier.
Rubbing defects and rubbing damage are less likely to occur, and display characteristics are improved.

Furthermore, in the manufacturing method of this example, the photosensitive polyimide 10 is exposed from the back side of the glass substrate 1 and the gate electrode @2 is used as a mask, so there is no need to prepare a separate photomask, and the manufacturing process The process is simple.

4 and 5 relate to a method of manufacturing a display device according to another invention, FIG. 4 is a plan view showing one pixel of the manufactured display device, and FIGS. 5(a) to (f) 4 is a process explanatory diagram showing the manufacturing process of the TPT portion (cross section taken along the line I-n) in FIG. 4 in the left column and the electrode busbar portion (cross section taken along the line II-n) shown in FIG. 4 in the right column. FIG.

This embodiment will be explained below based on FIG. 4 and FIGS. 5(a) to 5(f). First, as shown in FIG. 5(a), the gate electrode 22 and the electrode busbar 22a are formed on the surface of the glass substrate 21.

Next, as shown in FIG. 2B, a negative photosensitive polyimide 30 is applied onto the glass substrate 21 so as to cover the gate electrode 22 and the electrode busbar 22a, and after prebaking, the gate electrode 22 is A photomask M having a black pattern is overlapped on the part where the electrode busbar 22a intersects with the drain electrode busbar, and ultraviolet rays are applied from above the photomask M.
Exposure with I is performed.

Next, as shown in FIG. 3(c), the glass substrate 22 is exposed to ultraviolet light UV2 from the back side. There is a certain relationship between the remaining film thickness T of the photosensitive polyimide 30 after finishing the process, and in this example, the coating film of the photosensitive polyimide 30 is determined based on the results of measuring this relationship in advance. Thickness and UV resistance
Determine the exposure amount of Vl and UV2.

Next, the photosensitive polyimide 30 is ultrasonically developed using a developer, and as shown in FIG. After removing polyimide 30, performing ultrasonic rinsing, and drying, the
．． The photosensitive polyimide 30 is temporarily cured by heating for 5 to 1 hour.

Next, the glass substrate 21 provided with the gate t[i22 and whose surface is covered with the photosensitive polyimide 30 is immersed in an electrolytic solution to remove the surface of the gate electrode 22 and the electrode bus bar 22.
Anodize the exposed portion of a.

Then, as shown in FIG. 2(e), the gate electrode 22
A first gate insulating layer 23 is formed thereon, and a similar insulating layer 23a is formed also on the electrode bus bar 22a, thereby reducing the thickness of the electrode bus bar 22a.

Thereafter, the photosensitive polyimide 30 is cured by heat treatment at 400 to 500°C for 0.5 to 1.0 hours.

Next, as shown in Figure (f), silane (S i H,s ) and ammonia (N
Silicon nitride film (SiN) using H3) as source gas
forming a second gate insulating layer 24 made of amorphous silicon (a-8L) using silane as a raw material gas above the gate electrode 22 on the second gate insulating layer 24; An ohmic contact layer 2 made of amorphous silicon (n"-a-8t) to which phosphorus is added is formed using silane and phosphine (PH3) as raw material gases, and a source electrode 27 and a drain electrode 2 are formed.
form 8. Then, a portion of the ohmic contact layer 26 located between the source electrode 27 and the drain electrode 28 is removed to form a pixel electrode 29 made of ITO.

According to the manufacturing method of the embodiment described above, the first gate insulating layer 23 and the semiconductor active layer 25 can be formed flat for the same reason as the embodiment of FIG. The sauce formed by @[! 27 and the drain electrode 28 can be made small, disconnection of the source electrode 27 and drain electrode 28 is less likely to occur, and alignment processing is facilitated, so rubbing defects and rubbing damage are less likely to occur, and display characteristics are improved. Become.

Furthermore, in this embodiment, the thickness of the electrode bus bar 22a can be made thinner at the same time as TPT manufacturing (fifth same left column side), and the wiring resistance of the electrode bus bar 22a can be easily set.

〔Effect of the invention〕

As explained above, according to the manufacturing method of the present invention, the semiconductor active layer can be formed flat on the first gate insulating layer and the photosensitive polyimide, and the source electrode and the train electrode can be formed thereon, so that the difference in level can be reduced. It can be made smaller, and disconnection of the source and drain electrodes is less likely to occur. Furthermore, since the step is small, the alignment treatment when an alignment treatment film is formed thereon becomes easy, and rubbing defects and rubbing damage are less likely to occur, resulting in the effect of improving display characteristics.

Furthermore, according to another invention, in addition to the above-mentioned effects, the wiring resistance of the electrode bus bar can be easily set, and the manufacturing method can be simplified.

[Brief explanation of drawings]

FIGS. 1(a) to (e) are process explanatory diagrams for explaining one embodiment of the method for manufacturing a display device according to the present invention, and FIGS. 2(a-) to (f) are diagrams of a conventional display device. 3 is a cross-sectional view showing a case where the TPT and pixel electrode manufactured by the method shown in FIG. 1 are incorporated into an active matrix liquid crystal display as a display device; FIG. 4 is a process explanatory diagram for explaining the manufacturing method; FIG. Plan views showing one pixel of a display device manufactured by a method according to another invention, FIGS. The electrode busbar part in Figure 4 is shown in the right column (
It is a process explanatory diagram which shows the manufacturing process of I [-II line cross section). 1.21... Glass substrate, 2.22... Gate electrode, 22a... Electrode bus bar, 3.23... First gate insulating layer, 23a... Insulating layer, 4.24... Second gate insulating layer, 5.25... Semiconductor active layer, 6.26... Ohmic contact layer, 7.27... Source electrode, 8.28... Drain electrode, 9.29... Pixel electrode, 10.30...photosensitive polyimide.

Claims (2)

[Claims] (1) A step of forming a gate electrode made of a metal that can form an insulator by anodic oxidation on the surface of a transparent insulating substrate, and forming a negative photosensitive polyimide on the substrate so as to cover the gate electrode. a step of exposing the photosensitive polyimide from the back side of the substrate; and a step of developing the photosensitive polyimide and removing only the unexposed portion of the photosensitive polyimide on the gate electrode. a step of forming a first gate insulating layer by anodizing the surface of the gate electrode; a step of curing the photosensitive polyimide by heat treatment; and a step of curing the photosensitive polyimide and the first gate insulating layer. forming a second gate insulating layer on the second gate insulating layer; a semiconductor active layer, a source electrode on the second gate insulating layer;
1. A method for manufacturing a display device, comprising the step of forming a drain electrode and a pixel electrode. (2) forming, on the surface of the transparent insulating substrate, an electrode bus bar made of a metal capable of forming an insulator by anodic oxidation, and a gate electrode connected to the electrode bus bar; and a step of applying negative photosensitive polyimide to cover the gate electrode, applying a photomask covering a part of the electrode bus bar and the gate electrode to the front side of the substrate, and applying the photomask from above the photomask. a step of subjecting the photosensitive polyimide to a first exposure; a step of subjecting the photosensitive polyimide to a second exposure from the back side of the substrate; and developing the photosensitive polyimide to remove the photosensitive polyimide on the electrode busbar. The thickness of the electrode busbar is reduced by removing the photosensitive polyimide on the unexposed part and the gate electrode, and anodizing the part of the electrode busbar not covered with the photosensitive polyimide and the gate electrode. a step of thinning the gate electrode and forming a first gate insulating layer on the gate electrode; a step of heat-treating and curing the photosensitive polyimide; forming a second gate insulating layer on the insulating layer and the first gate insulating layer; a semiconductor active layer, a source electrode on the second gate insulating layer;
1. A method for manufacturing a display device, comprising the step of forming a drain electrode and a pixel electrode.