Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Including integrally formed optical element
Reissue Patent
2002-10-03
2004-03-16
Lebentritt, Michael S. (Department: 2824)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Including integrally formed optical element
C438S158000, C438S160000, C438S486000, C438S949000
Reissue Patent
active
RE038466
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing an active matrix substrate using a method of transferring a thin film device. The present invention also relates to an active matrix substrate manufactured by the manufacturing method, and a liquid crystal display device comprising this active matrix substrate as one of a pair of substrates.
2. Description of Related Art
For example, a liquid crystal display using thin film transistors (TFT) is manufactured through the step of forming thin film transistors on a substrate by CVD or the like. Since the step of forming thin film transistors on the substrate is accompanied with high temperature processing, it is necessary to use material for the substrate which has excellent heat resistance, i.e., material having a high softening point and melting point. At present, silica glass is used as a substrate which can resist a temperature of about
10000
C, and heat resistant glass is used as a substrate which can resist a temperature of about 500° C.
Namely, the substrate on which thin film elements are mounted must satisfy conditions for producing the thin film transistors. Therefore, the substrate used is determined so as to satisfy conditions for manufacturing a device to be mounted thereon.
However, in consideration of only the steps after the substrate comprising the thin film transistors such as TFT or the like mounted thereon is completed, in some cases, the above-described substrate is not always satisfactory.
For example, in the above-described manufacturing process accompanied with high temperature processing, a quartz substrate, a heat-resistant substrate, or the like is used. However, these substrates are very expensive, and thus cause an increase in product cost.
Also the glass substrate has the properties that it is heavy and easily broken. A liquid crystal display used for portable electronic apparatus such as a palm top computer, a portable telephone, etc. is preferably light weight, can resist a little deformation, and is hardly broken by dropping. However, in fact, the glass substrate is generally heavy, less resistant to deformation and is possibly broken by dropping.
In other words, there are gaps between the limitations caused by manufacturing conditions and preferable characteristics required for products, and it is very difficult to satisfy the conditions and characteristics.
SUMMARY OF THE INVENTION
The present invention has been achieved in consideration of these problems, and an object of the invention is to provide a novel technique which permits independent free selection of a substrate used in producing thin film devices, and a substrate (a substrate having preferable properties for application of a product) used in, for example, actual use of a product, and a completely new method of effectively manufacturing an active matrix substrate having excellent properties and a liquid crystal display device by using the technique.
In order to achieve the object, the present invention may include the following.
(1) The present invention provides a method of manufacturing an active matrix substrate comprising a pixel portion including thin film transistors connected to scanning lines and signal lines arranged in a matrix, and pixel electrodes respectively connected to terminals of the thin film transistors, the method may include:
forming a separation layer on the substrate;
forming the thin film transistors over the separation layer;
forming an insulation film on the thin film transistors and over the separation layer;
selectively removing at least a portion of the insulation film in a region where each of the pixel electrodes is to be formed;
forming each of the pixel electrodes on the insulation film and the separation layer in a region where at least a portion of the insulation film has been removed;
adhering the thin film transistors to a transfer material with an adhesive layer
producing exfoliation in the separation layer and/or at an interface of the separation layer and the substrate to separate the substrate from the separation layer; and
removing any portion of the separation layer remaining on the pixel electrodes and under the insulation film to form an active matrix substrate using the transfer material as a new substrate.
In the method of manufacturing an active matrix substrate of the present invention, the thin film transistors and the pixel electrodes formed on the substrate are transferred to the desired transfer material by the device transfer technique developed by the applicant of the present invention. In this case, the device transferred onto the transfer material is reverse to a normal device. In the transferred device, consequently, the pixel electrode is covered with the insulator layer such as an interlayer insulation film or the like before transfer. If the insulation film has a large thickness, a large voltage loss occurs in this portion, and thus a sufficient voltage cannot be applied to a liquid crystal.
Therefore, in the manufacturing method of the present invention, in forming the thin film transistors and pixel electrodes on the original substrate before transfer, at least a portion of the insulator layer such as the interlayer insulation film or the like is removed before the pixel electrodes are formed. In this case, the entire insulator layer is preferably removed. However, when the insulation film remaining unremoved is thin, at least a portion of the insulator layer may be removed because no problem occurs in application of a voltage to the liquid crystal.
In any case, by separating the original substrate after a device is transferred onto the transfer material, the pixel electrode partially appears at least in the vicinity of the surface of the device. Therefore, a sufficient voltage can be applied to the liquid crystal layer from this portion.
The insulation film remaining on the pixel electrodes can also be separately removed in another step (for example, in a step after transfer of the device).
(2) The present invention provides a method of manufacturing an active matrix substrate comprising a pixel portion including thin film transistors connected to scanning lines and signal lines arranged in a matrix, and pixel electrodes respectively connected to terminals of the thin film transistors, and the method may include:
forming a separation layer on a substrate;
forming an intermediate layer on the separation layer;
forming the thin film transistors on the intermediate layer;
forming an insulation film on the thin film transistors and the intermediate layer;
selectively removing a portion of the insulation film in a region where each of the pixel electrodes is to be formed;
forming each of the pixel electrodes on the insulation film and the separation layer in the region where at least a portion of the insulation film is removed;
adhering the thin film transistors to a transfer material with an adhesive layer;
producing exfoliation in the separation layer and/or at an interface of the separation layer and the substrate to separate the substrate from the separation layer; and
removing any portion of the separation layer remaining on the intermediate layer and the pixel electrodes to form an active matrix substrate using the transfer material as a new substrate.
This invention is different from invention (1) in that the intermediate layer is provided. The intermediate layer can comprise a single layer film of an insulator, such as an SiO
2
film or the like, or a multilayered film comprising a laminate of an insulator and a metal. The intermediate layer functions to facilitate separation from the separation layer, protect the transistors from contamination during removal of the separation layer, ensure insulation properties of the transistors, and suppress irradiation of the transistors with laser light.
In forming the thin film transistors and the pixel electrodes on the original substrate before transfer, at least a portion of the insulator layer such as an interlayer insulation film or the like, which causes a prob
Inoue Satoshi
Shimoda Tatsuya
Lebentritt Michael S.
Oliff & Berridg,e PLC
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