Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate – On insulating substrate or layer
Reexamination Certificate
2003-02-13
2004-05-18
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
On insulating substrate or layer
C438S030000, C438S066000, C438S067000, C438S070000, C438S082000, C438S099000, C438S128000, C438S149000, C438S456000, C438S587000, C438S669000, C438S708000, C438S715000, C438S716000, C438S778000, C438S482000, C438S949000
Reexamination Certificate
active
06737338
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a pattern forming method for forming a predetermined pattern by a photolithography method on a plastic substrate which composes a display device such as a liquid crystal display device, an organic EL display device, an electrophoresis display device, etc., and a display device manufactured using the same.
BACKGROUND OF THE INVENTION
When a predetermined pattern is formed by a photolithography method on a substrate which composes a display device, the pattern is often required to be formed with high accuracy of dimension and position. For example, in a case of a pair of substrates which compose a liquid crystal display device, a transparent conductive film composed of Indium Tin Oxide (ITO) having a predetermined pattern is formed on each of the substrates, and then the pair of substrates are pasted with each other so that the both patterns face one another with predetermined accuracy of superposition. Thus, the predetermined patterns that are respectively formed on the substrates are required to be formed within a relatively constant range of dimensional accuracy.
Further, a color filter used for a liquid crystal display device is manufactured in such a manner that a plurality of patterns including a colored light-transmitting pattern of light's three primary colors such as RGB, a light-shielding pattern such as a black matrix, etc. are sequentially formed. Thus, the respective patterns are required to be formed within a constant range of accuracy of superposition. The accuracy of superposition here is mainly achieved by relative accuracy of dimension and position among the respective formed patterns. The higher definition of a manufactured color filter pattern requires higher accuracy of superposition, and thus requires higher accuracy of dimension and position for each of the formed patterns. Further, a transparent electrode for liquid crystal driving composed of ITO is required to be formed on the color filter with the same accuracy.
For example, when the formed pattern of the color filter and the formed pattern of the ITO for liquid crystal driving are both formed with high accuracy of dimension and position, the both patterns are formed with fine accuracy of superposition over an entire substrate, so that each of driving ITOs
101
corresponds to one color of color filters R•G•B, as shown in FIG.
11
(
a
). In contrast, when the accuracy of dimension and position is not good, positional misalignment occurs. When the accuracy of superposition of the both patterns is not good, namely an amount of the positional misalignment exceeds a tolerance, a so-called color mixture defect occurs, in which one ITO
101
does not correspond to only one color of the color filters R•G•B, but corresponds to two or more adjacent colors of the color filters R•G•B. FIG.
11
(
b
) is an example where the color mixture defect occurs due to low accuracy of dimension, FIG.
11
(
c
) is an example where the color mixture defect occurs due to low accuracy of position, and FIG.
11
(
d
) is an example where the color mixture defect occurs due to low accuracy of both dimension and position.
Incidentally, a liquid crystal display device, etc., is generally manufactured in such a manner that a plurality of panel patterns are simultaneously formed in a large substrate, and, after undergoing various processes, the large substrate is separated into respective panels. The size of the substrate used is from approximately 300 mm square to not less than 1000 mm square. Thus, an entire surface of the substrate must satisfy the accuracy of dimension and position and the accuracy of superposition, which are required for forming the patterns.
Here, the accuracy of dimension and position for forming a pattern by a photolithography method is determined mainly at an exposing step, so that it largely depends on the performance of a developing device, photomask's accuracy of dimension and form, the performance of photosensitive resin, etc.
However, when the relative accuracy in superposition of a plurality of patterns is required, as in the above-described liquid crystal display device, required is not only the accuracy of dimension and position of the pattern that is formed at the exposing step. Even if the pattern can achieve high accuracy of dimension at the exposing step, when the substrate itself changes in dimension due to thermal expansion, etc., the dimensions of the already formed pattern also change. This causes a dimensional error between the pattern that is already formed and the pattern that is newly formed, thereby lowering accuracy of superposition between the respective formed patterns. Thus, at the exposing of the newly formed pattern, it is required to control the substrate dimensions so that the dimensions and form of the already formed pattern are retained.
Nowadays, as a substrate for a display device such as a liquid crystal display device, an organic EL display device, an electrophoresis display device, etc., a plastic substrate has come to be used instead of a conventional glass substrate. The plastic substrate has advantages over the glass substrate in terms of lightness in weight, shock resistance, flexibility, etc. However, the plastic substrate widely changes in dimension by a slight temperature change because of its high coefficient of thermal expansion. The plastic substrate also expands due to moisture absorption. As described above, the plastic substrate requires a higher level of technique of dimensional control, because the plastic substrate changes in dimension more than the glass substrate.
In order to control the dimensional change of the substrate due to the thermal expansion, the substrate temperature during the exposing should be controlled, so that general exposing devices have a structure capable of adjusting a substrate temperature. However, in order to achieve the accuracy of dimensional control of the plastic substrate same as that of the glass substrate, the exposing device must have about twice to tenth higher accuracy of adjusting the substrate temperature, depending on concrete materials and compositions of the plastic and the glass.
In order to control the dimensional change of the substrate due to the moisture absorption, it is highly effective to employ a method to control a moisture content of the substrate, such as inhibition of the moisture absorption using a hard-coat layer, dehydration of the substrate by heating, moisture absorption by rinsing, etc., as disclosed in Japanese Unexamined Patent Publication No. 6-186550/1994 (Tokukaihei 6-186550, published on Jul. 8, 1994), for example.
Incidentally, it is conventionally assumed that a dimensional behavior of the plastic substrate mainly depends on “the dimensional change due to the thermal expansion” and “the dimensional change due to the moisture absorption”; thus, when the pattern is formed by the photolithography method, it is assumed that the dimensional behavior of the plastic substrate can be controlled by “control of the substrate temperature at the exposing” and “control of the moisture content of the substrate at the exposing”, enabling the pattern formation with high accuracy of dimension and superposition.
However, the above-described pattern forming method has problems as described below.
Specifically, as to the method for the “control of the moisture content of the substrate at the exposing”, when the substrate is exposed after heated for reducing the moisture content of the substrate to a certain level, for example, the substrate may be arranged so as to include a moisture barrier layer such as a hard-coat layer, to inhibit the moisture absorption. This can reduce the speed of substrate expansion due to the moisture absorption after the end of the baking, and thus reduces the dimensional variations among the formed patterns due to the variations in exposing timing, thereby achieving the high accuracy of dimensional control.
The barrier layer for inhibiting the moisture absorption of the substrate is excel
Conlin David G.
Edwards & Angell LLP
Isaac Stanetta
Konieczny J. Mark
Niebling John F.
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