Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-04-22
2003-04-29
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C438S030000, C349S138000
Reexamination Certificate
active
06556264
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a liquid crystal display device (LCD), and particularly to a method of manufacturing an active matrix type liquid crystal display device using a semiconductor thin film (hereinafter referred to as an AM-LCD). The present invention can be applied to an electrooptical device equipped with such a display device.
Incidentally, in the present specification, the term “semiconductor device” indicates all devices which function by using a semiconductor. Thus, the foregoing display device and the electrooptical device are included in the category of the semiconductor device. However, in the present specification, for facilitation of the distinction, terms such as a display device and an electrooptical device are selectively used.
2. Description of the Related Art
In recent years, a projector or the like using the AM-LCD as a projection type display has been vigorously developed. Moreover, the demand of the AM-LCD as a direct viewing display for a mobile computer or a video camera is also increasing.
FIGS. 2A and 2B
schematically shows a structure of a pixel matrix circuit in a conventional active matrix type display device. Incidentally, the pixel matrix circuit is such a circuit that thin film transistors (TFTs) for controlling an electric field applied to a liquid crystal are arranged in matrix, and constitutes a picture image display region of the AM-LCD.
FIG. 2A
is a top view showing the pixel matrix circuit seen from the above. Here, regions surrounded by a plurality of gate lines
201
provided in the horizontal direction and a plurality of source lines
202
provided in the vertical direction become pixel regions. A TFT
203
is formed at each of the intersections of the plurality of gate lines
201
and the plurality of source lines
202
. A pixel electrode
204
is connected to each of the TFTs.
Thus, the pixel matrix circuit is constituted by the plurality of pixel regions formed in matrix by being surrounded by the plurality of gate lines
201
and the plurality of source lines
202
, and the TFT
203
and the pixel electrode
204
are provided at each of the pixel regions.
FIG. 2B
shows the structure of a section of the pixel matrix circuit. In
FIG. 2B
, reference numeral
205
denotes a substrate having an insulating surface,
206
and
207
denote pixel TFTs formed on the substrate
205
, which correspond to the TFTs
203
shown in FIG.
2
A.
The pixel TFTs
206
and
207
are connected to pixel electrodes
208
and
209
, respectively. The pixel electrodes
208
and
209
correspond to the pixel electrodes
204
shown in FIG.
2
A. The pixel electrodes
208
and
209
are generally obtained by patterning one metal thin film.
Thus, in the pixel matrix circuit of the conventional structure, boundary portions of electrodes (hereinafter simply referred to as boundary portions)
210
and
211
always exist between the pixel electrodes. That is, a difference in level, which corresponds to the film thickness of the pixel electrode, is inevitably formed. Poor orientation of a liquid crystal material occurs at such a difference in level, so that a displayed picture is disturbed. Besides, diffused reflection of incident light at the portion of the difference in level causes the contrast to lower or the efficiency of utility of light to lower.
As is apparent from
FIG. 2B
, the pixel electrodes
208
and
209
formed over the semiconductor elements or the intersections of the respective wiring lines have the state reflecting the shape of the semiconductor elements and the intersections. Such a difference in level also causes the foregoing problems.
Particularly, in a projection type display used for a projector or the like, since an extremely minute small display of about 1 to 2 inches in size is enlarged and projected, the foregoing problems become tangible.
In regard to the above described problems, a black mask (or a black matrix) has been conventionally used to shade the region where a picture image is disturbed, so that the ratio of contrast is increased. In recent years, since miniaturization of a device has been progressed and the controllability of a shading region for the purpose of a high aperture factor has been required, the structure in which the black mask is provided at a TFT side substrate has become the main stream.
However, in the case where the black mask is provided at the TFT side substrate, there arises various problems such as increase of patterning steps, increase of parasitic capacitance, and lowering of an aperture factor. Because of such circumstances, it is desired to achieve a technique by which the ratio of contrast can be assured without causing the above described problems.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to solve the above-mentioned problems and to provide means for forming an extremely fine active matrix type display device by a simple process.
In order to achieve the above object, according to one aspect of the present invention, a method of manufacturing a semiconductor device comprises the steps of: flattening an insulating film formed on a substrate having an insulating surface; forming a plurality of electrodes on the insulating film; forming an insulating layer covering the plurality of electrodes; and flattening the surfaces of the plurality of electrodes and the surface of the insulating layer so that both the surfaces form the same plane, and boundary portions of the plurality of electrodes are filled with the insulating layer, wherein the flattening step is carried out with a precision of not larger than 20% of a thickness of the electrodes.
According to another aspect of the present invention, a method of manufacturing a semiconductor device including at least a first substrate, a transparent second substrate, and a liquid crystal layer held between the first substrate and the second substrate, the method comprising the steps of: flattening an insulating film formed on the first substrate; forming stripe-shaped electrodes on the insulating film; forming an insulating layer covering the stripe-shaped electrodes; and flattening the surfaces of the stripe-shaped electrodes and the surface of the insulating layer so that both the surfaces form the same plane, and boundary portions of the stripe-shape electrodes are filled with the insulating layer, wherein the flattening step is carried out with a precision of not larger than 20% of a thickness of the electrodes.
According to still another aspect of the present invention, a method of manufacturing a semiconductor device comprises the steps of: forming a plurality of semiconductor elements on a substrate having an insulating surface; forming an interlayer insulating film; flattening the interlayer insulating film; forming pixel electrodes electrically connected to the semiconductor elements on the interlayer insulating film; forming an insulating layer covering the pixel electrodes; and flattening the surfaces of the pixel electrodes and the surface of the insulating layer so that both the surfaces form the same plane, and boundary portions of the pixel electrodes are filled with the insulating layer, wherein the flattening step is carried out with a precision of not larger than 20% of a thickness of the electrodes.
According to still another aspect of the present invention, a method of manufacturing a semiconductor device including at least a substrate having a plurality of semiconductor elements formed in matrix and a plurality of pixel electrodes respectively connected to the semiconductor elements, and a liquid crystal layer held on the substrate, the method comprising the steps of: forming an interlayer insulating film; flattening the interlayer insulating film; forming pixel electrodes electrically connected to the semiconductor elements on the interlayer insulating film; forming an insulating layer covering the pixel electrodes; and flattening the surfaces of the pixel electrodes and the surface of the insulating layer so that bo
Hirakata Yoshiharu
Yamazaki Shunpei
Parker Kenneth
Robinson Eric J.
Robinson Intellectual Property Law Office P.C.
Semiconductor Energy Laboratory Co,. Ltd.
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