Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2003-01-22
2004-12-07
Niebling, John F. (Department: 2812)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C359S245000, C377S019000, C377S020000, C377S028000, C377S029000, C385S002000, C385S008000
Reexamination Certificate
active
06828817
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an electrooptic device and an electronic apparatus having many electrical elements formed on a substrate that supports an electrooptic material. The invention also relates to a method for making such an electrooptic device. Specifically, the invention relates to examining electrical characteristics of the electrical devices formed on the substrate.
2. Description of Related Art
In related art electrooptic devices, such as liquid crystal devices and organic electroluminescent devices, many switching elements are formed on a substrate supporting an electrooptic material.
An example of such an electrooptic device is an active matrix liquid crystal device employing thin film transistors, hereinafter “TFTs,” as the pixel switching elements. In making the device, as shown in
FIG. 20
, components of a plurality of TFT array substrates
10
are formed on a large substrate
10
e
, and the large substrate
10
e
is cut along cutting lines
10
f
so as to prepare individual TFT array substrates
10
used in liquid crystal devices.
The regions sandwiched by the cutting lines
10
f
are generally used in the related art as inspection regions
10
g
to inspect pixel-switching TFTs
30
formed in a matrix inside pixel regions
10
a
of the TFT array substrates
10
and to inspect driving-circuit TFTs (not shown) that constitute driving circuits
101
and
104
, as shown in FIG.
21
.
In other words, the pixel-switching TFT
30
is formed in each of the pixels arranged in a matrix on each TFT array substrate
10
. When the TFT array substrate
10
is of an internal driving circuit type, the driving circuits
101
and
104
are constituted from TFTs (not shown). In the related art, the process for forming these TFTs is also used to form an inspection TFT
30
g
′ functioning as an inspection pattern, a first inspection pad
31
g
′ electrically connected with a drain region of the inspection TFT
30
g
′, a second inspection pad
32
g
′ electrically connected with a source region of the inspection TFT
30
g
′, and a third inspection pad
33
g
′ electrically connected with a gate electrode of the inspection TFT
30
g
′ within the inspection region
10
g
. These processes are performed onto the large substrate
10
e
shown in
FIG. 20
, and one inspection TFT
30
g
′ is formed in the inspection region
10
g
near one TFT array substrate
10
(one-to-one correspondence).
The electrical characteristics of the inspection TFTs
30
g
′ are examined by bringing inspection terminals into contact with the inspection pads
31
g
′,
32
g
′, and
33
g
′ while they are mounted on the large substrate
10
e
. If the electrical characteristics of the inspection TFT
30
g
′ are satisfactory, those of the pixel-switching TFTs
30
formed in the corresponding TFT array substrate
10
are assumed to be satisfactory, and the TFT array substrate
10
is assembled into a liquid crystal device. On the other hand, if the inspection TFT
30
g
′ is found to be defective, the pixel-switching TFTs
30
formed in the corresponding TFT array substrate
10
are assumed to be defective, and this TFT array substrate
10
is discarded. As a result, the yield can practically be increased. Moreover, the position in the large substrate
10
e
that is likely to suffer from defects can be detected, and the results can be easily reflected in the manufacturing process.
SUMMARY OF THE INVENTION
However, in the related art, the region where the inspection TFT
30
g
′ is formed is distant from the region where the pixel-switching TFTs
30
and driving-circuit TFTs are formed. This is because the inspection TFT
30
g
′ is formed outside the region of the TFT array substrate
10
, although the inspection TFT
30
g
′ is formed near the region where the TFT array substrate
10
is formed in the large substrate
10
e.
Accordingly, when the TFTs are formed using the semiconductor process, the results at the inspection TFT
30
g
′ may not correspond with the quality of the pixel-switching TFTs
30
and the driving-circuit TFTs due to variation in the characteristics of the TFTs resulting from the position in the substrate. Moreover, the pattern density in the region where the pixel switching TFT
30
g
and the driving-circuit TFTs are formed is significantly different from the pattern density in the region where the inspection TFT
30
g
′ is formed. Thus, when the TFTs are made using the semiconductor process, for example, the influence of the pattern density on exposure is significantly different between the region where the pixel-switching TFTs
30
and the driving-circuit TFTs are formed and the region where the inspection TFT
30
g
′ is formed. Because of this, in some cases, the inspection results at the inspection TFT
30
g
′ do not reflect the quality of the pixel switching TFTs
30
and the driving-circuit TFTs.
To address or overcome these problems, the present invention provides an electrooptic device and an electronic apparatus, in which electrical characteristics of many thin-film switching elements formed on a substrate to support an electrooptic material can be reliably inspected. The invention also provides a method for making the electrooptic device.
To address or overcome the above-described problems, the present invention provides an electrooptic device including a substrate to support an electrooptic material and an electrical-element-forming region formed on the substrate and including many thin-film switching elements, in which an inspection pattern to examine characteristics of the thin-film switching elements and inspection pads electrically connected to the inspection pattern are formed inside the electrical-element-forming region.
Moreover, the preset invention also provides a method for making an electrooptic device including a substrate to support an electrooptic material and an electrical-element forming region formed on the substrate and including many thin-film switching elements. The method includes forming an inspection pattern to inspect the electrical characteristics of the thin-film switching elements inside the electrical-element forming region simultaneously with forming the thin-film switching elements inside the electrical-element-forming region of the substrate, and forming inspection pads electrically connected to the inspection pattern; examining the electrical characteristics of the inspection pattern by placing inspection terminals into contact with the inspection pads; and manufacturing the electrooptic device using the substrates that have been determined to have satisfactory quality as a result of inspection.
In this invention, the inspection pattern to examine the thin-film switching element formed inside the electrical-element-forming region is formed inside the electrical-element-forming region, so that the thin film switching element to be examined and the inspection pattern used in actual measuring are disposed nearby. Thus, when thin-film switching elements, such as TFTs, are formed in a substrate by a semiconductor process, the electric characteristics of the thin-film switching element to be examined accurately corresponds with the electrical characteristics of the inspection pattern used in actual measuring, even when the characteristics of the TFT vary depending on the positions in the substrate. Moreover, the conditions, such as pattern density, are the same between the region where the thin-film switching elements, i.e., the objects of the inspection, are formed and the region where the inspection pattern is formed. This is because the inspection pattern used in actual inspection is formed in the electrical-element-forming region. Thus, for example, the effect of exposure on the pattern density is the same between the region where the thin-film switching element to be examined are formed and the region where the inspection pattern is formed. Thus, the correspondence between the elect
Isaac Stanetta
Niebling John F.
Oliff & Berridg,e PLC
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