JP2001526412A - Fabrication of a matrix composed of thin-film transistors with storage capacitors - Google Patents

Abstract

(57) Abstract: In order to reduce the number of process steps for the passivation of the matrix and to manufacture the pixel electrodes, respectively, use optically structurable materials, in particular for liquid crystal displays. A method for producing a matrix of thin film transistors with storage capacitors is proposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

The invention starts from the process of producing a matrix of thin-film transistors with storage capacitors in the field of the independent claims, in particular for liquid-crystal displays.

From DE 43 10 640 C1 and DE 43 39 721 A1, respectively, the production of a matrix of thin-film transistors with storage capacitors for a liquid crystal display is known, in which case the number of mask steps required by photolithography is reduced to three.
Alternatively, by reducing the number to 4, manufacturing costs can be reduced. In a known method as a semiconductor for a thin film transistor, a-Si: H is used. However, no reduction in manufacturing costs for manufacturing a thin film transistor matrix by omitting other process steps, such as etching, coating and cleaning, is not planned in this way.

Advantages of the invention The method of the invention with the features of the independent claims has the advantage over known methods that fewer coating, etching and photo-lacquering steps are required.

This is achieved by using optically structurable materials, respectively, for passivating the matrix and for producing the pixel electrodes. In contrast to known methods using SiN _x as passivation and usually ITO as pixel electrodes, respectively, the coating step, namely the PEC VD method for SiN _x and the sputtering of ITO, respectively, is now carried out in the etching step, ie in each case using the ITO step. It is possible to omit the dry etching of SiN _x and the wet etching of ITO, and a step for cleaning the photo-lacquer mask and a device therefor, respectively.

[0005] Advantageous developments and improvements of the method described in the independent claim are possible with the method described in the dependent claims.

For example, it is particularly advantageous to use polymers as photostructurable materials.
In this case, a highly insulating photosensitive transparent polymer can be used for passivation, and a conductive polymer can be used for manufacturing a pixel electrode.

[0007] The mechanical polishing of the conductive polymer further allows for the alignment of the liquid crystal, so that the application of an additional alignment layer, for example polyimide, can be omitted altogether.

In one advantageous process, the individual steps are as follows: The first conductive layer is applied as a row of a thin-film transistor matrix, as a gate-contact of a transistor and as an electrode of a storage capacitor. Applying and structuring; applying a gate-insulator; applying a semiconductor; applying a P-type or N-type doped semiconductor as a drain and source contact of the transistor; a thin film transistor; Applying another conductive layer for the columns of the matrix, for the drain and source contacts and the counter electrode of the storage capacitor,
And structuring the doped and undoped semiconductor layers;-applying, exposing and developing an insulating photosensitive transparent material;-an insulating photosensitive transparent. Apply material and expose.

In this case, advantageously, a-Si is used as the semiconductor and SiN is used as the gate insulating layer. _x Can be used.

[0010] With a considerable reduction in the number of process steps, a clear cost reduction and at the same time an increase in the yield can be achieved.

Drawings Embodiments of the present invention are shown in the drawings and are described in detail in the following description. FIG. 1 shows cross-sectional views of a liquid crystal display pixel at various stages of manufacture.

In the manufacturing stage according to FIG. 1 a), a first metallization layer 11
For example, 200 nm MoTa is sputtered and structured as row lines and as storage capacitor wiring. Subsequently, the gate insulating layer 12, for example, 35
0NmSiN _x, intrinsic semiconductor 13, for example 150nmi-a-Si and high-Doping semiconductor 14, for example, 50nm n ⁺ -a-Si and the coating metal layer (Deckmetall
iserung), for example a layer sequence of 200 nm Mo is applied.

FIG. 1 b) shows the covering metallization layer 15 and the doping layer 14 as column wiring, drain / source contacts D, S and the covering electrode of the storage capacitor C (Deckelektrode).
) Shows the structure after etching.

In the method step of FIG. 1c), the semiconductor layer 13 and the gate dielectric 12 are used in a single plasma etching step to divide the individual thin-film transistors of the pixel and to expose the connection areas of the gate lines and the storage capacitor lines. Manufactured to let.

In FIG. 1 d), a highly conductive photosensitive transparent polymer 16 has been applied, exposed, developed and heat treated. As a polymer, for example, so-called photo-BCB
Can be used. The challenge with polymers is to passivate and planarize the structure. Here, at the same time, the covering electrode of the storage capacitor C, which is the drain-contact of the thin film transistor, and the connection region of the column line and the row line are exposed again in the polymer exposure step and the development step.

In FIG. 1 e), a conductive photosensitive transparent polymer 17 is subsequently applied as a pixel electrode. For this purpose, for example, a polymer with the trade name PEDT / PSS from Bayer AG can be used. When a region between pixel electrodes is exposed to light using UV light through a photomask, the conductive polymer is changed into an insulating layer. The insulating region of the polymer is shown in FIG.
) Are shown dotted. When using conductive photopolymer,
The region between the pixel electrodes can be removed by a developer step. The individual pixel electrodes can also be effectively and electrically separated from each other. The unexposed regions of the pixel electrode have a transparency of> 70% in the visible region at a layer resistance per area of 200-1000Ω and a dry film thickness of 900 nm after a heat treatment step of the polymer PEDT / PSS at about 130 ° C. By reducing the dry film thickness, the transmittance can be increased. Layer 1
7 may subsequently be mechanically polished to provide liquid crystal alignment. This allows
The application of an additional alignment layer can also be omitted.

The structuring of the gate dielectric 12 can be carried out with the structuring of the undoped semiconductor 13 as shown, or with an additional plasma etching process together with the passivation layer 16 as masking. .

[Brief description of the drawings]

FIG. 1 illustrates a cross-sectional view of a liquid crystal display pixel at various stages of manufacture according to one embodiment of the present invention.

[Explanation of symbols]

C storage capacitor, D and S drain and source-contact, G
Gate-contact, 10 first conductive layer, 12 gate insulating layer, 13
Undoped semiconductor, 14 p-type or n-type doped semiconductor, 15 another conductive layer, 16 highly insulating photosensitive transparent material, 17 conductive photosensitive transparent material

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] February 29, 2000 (2000.2.29)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

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Claims (7)

[Claims] 1. A method for producing a matrix comprising thin-film transistors with storage capacitors (C), in particular for liquid crystal displays, in each case being optically structurable for the passivation of the matrix and for the production of the pixel electrodes. A method for producing a matrix comprising thin film transistors with storage capacitors, characterized in that the use of a simple material (16, 17). 2. The method according to claim 1, wherein the photostructurable material is a polymer. 3. A highly insulating photosensitive transparent polymer for passivation.
The method according to claim 2, wherein the conductive polymer (17) is used for the production of the pixel electrode. 4. The method according to claim 3, wherein the liquid crystal is aligned by mechanically polishing the conductive polymer (17). 5. The following steps: a first conductive layer (1) as a thin-film transistor matrix row, as a transistor gate-contact (G) and as an electrode of a storage capacitor (C);
0) applying and structuring;-applying a gate-insulator (12);-applying a semiconductor (13);-drain- and source-transistors of the transistor as P-type as contacts (D, S). Or applying an N-doped semiconductor (14), for the columns of the thin film transistor matrix, for the drain and source contacts (D, S) and for the counter electrodes of the storage capacitors (C). Applying and structuring one conductive layer (15), a doped semiconductor layer (14) and an undoped semiconductor layer (
13) structuring,-applying, exposing and developing an insulating photosensitive transparent material (16);-applying and exposing a conductive photosensitive transparent material (17); The method according to any one of claims 1 to 4. 6. A semiconductor device comprising a-Si: H as a semiconductor and Si as a gate insulating layer.
6. The process according to claim 5, wherein _Nx is used. 7. The method according to claim 5, wherein the gate insulating layer is structured in a separate step with the photo-structurable passivation layer as a mask.