Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2001-10-26
2004-12-28
Pert, Evan (Department: 2829)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
Reexamination Certificate
active
06836140
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method for manufacturing a display device, and a substrate for the same. More particularly, the present invention relates to a method for manufacturing an active matrix liquid crystal display device (LCD) such as LCDs of TFT (Thin Film Transistor) type and MIM (Metal-Insulator-Metal) type, and a substrate used to manufacture the same.
2. Description of the Background Art
Recent improvement in performance of the display devices requires stricter management of the device characteristics. Management of the device characteristics is necessary for quality control, early detection of defective substrates, and prevention of outflow of such detective substrates into the process. For example, a TFT substrate of the LCD is fabricated by the process including a plurality of thin-film deposition steps and a plurality of patterning steps. In order to evaluate the manufacturing process and the like, characteristics such as TFT characteristics, bus line resistance and contact resistance are evaluated. One such evaluation method is to provide on a TFT substrate a TEG (Test Element Group) including test elements according to the purpose of evaluation, and measure characteristics of each test element by making a probe in contact with a terminal connected to that test element (for example, see Japanese Laid-Open Publication No. 8-190087, and in particular,
FIGS. 1 and 2
thereof).
Since there exist various types of LCDs, kinds of characteristics to be evaluated and the number of such characteristics vary depending on the type of the LCD. In addition, kinds of test elements of the TEG and the number of such test elements also vary depending on the type of the LCD. For example, in the case of a TFT substrate having an organic insulation film entirely covering a picture element, characteristics associated with the organic insulation film are evaluated in addition to the characteristics that are evaluated for a TFT substrate having no organic insulation film. Moreover, since there are many sizes of the LCDs, the number of TEGs and their positions may be limited from the standpoint of the design. Recently, in order to manufacture many types of LCDs efficiently, the LCDs having different panel sizes are sometimes manufactured from the same mother substrate in the same production line. In other cases, the LCDs having different panel sizes are manufactured from the respective mother substrates having the same size. Since the position of the TEG and characteristics to be tested vary depending on the type of the LCD, separates probes are required for the respective types of the LCDs. In other words, expensive probes must be prepared in order to test the respective types of the LCD. Accordingly, a plurality of test apparatuses must be prepared for the respective types of the LCDs. Alternatively, when the same test apparatus is used, a probe must be replaced every time the type of the LCD is changed, complicating the manufacturing process. Moreover, the time to replace the probe is required, reducing the production efficiency.
In the recent display devices, the space for the TEG on the substrate has been increasingly reduced. The first reason for this is to reduce the production costs. In order to reduce the production costs, as many substrates as possible must be obtained from a single mother substrate. This requires the substrate area other than the display portion to be reduced as much as possible. Recently, the display devices tend to be specially developed for the medium- or small-size applications. Therefore, this is remarkable particularly in a small-size substrate for use in mobile products. The second reason is narrowing of the frame in the recent display devices. In order to narrow the frame portion (the portion other than the display portion) as much as possible, required terminals (such as drivers) and TEG must be formed in a narrow region. Accordingly, there is a need for development of a TEG efficiently integrating the test elements.
It is an object of the present invention to provide a display device substrate capable of being inexpensively evaluated with high operating efficiency, and thus achieving improved production efficiency. It is another object of the present invention to provide a method for manufacturing a display device with high production efficiency using a production line for manufacturing different types of display devices. In other words, it is another object of the present invention to efficiently manufacture various display devices in the same production line.
SUMMARY OF THE INVENTION
(1) According to the present invention, a method for manufacturing a display device using a production line for manufacturing at least two different types of display devices includes the steps of: fabricating a circuit substrate including a display device circuit of the display device and a plurality of test elements for evaluating characteristics of a circuit element forming the display device circuit; and evaluating the characteristics of the circuit element, the evaluating step including the step of measuring characteristics of the plurality of test elements formed on the circuit substrate, wherein each of the plurality of test elements is connected to at least one of a plurality of test terminals arranged with a common pattern in the at least two different types of display devices, and the measuring step is conducted with a common probe being in contact with the at least one test terminal regardless of the type of the display device.
Note that the phrase “different types” as used herein implies not only the difference in size of the display device and the difference in type of the circuit element forming the display device circuit but also the difference in manufacturing process of the circuit element, and the like. The term “circuit substrate” refers to a substrate having a plurality of circuit elements formed thereon, such as a TFT substrate and an MIM substrate (hereinafter, sometimes referred to as “display device substrate”). The term “test element” indicates an element formed in a free region on the substrate other than the region occupied by the display device circuit. The term “display device circuit” indicates the overall circuitry required for operation as a display device, and includes not only picture-element electrodes in the display region, switch elements such as TFTs, wiring portions such as bus lines, and terminal portions, but also driving circuitry for driving the switch elements. The phrase “a plurality of test terminals arranged with a common pattern” means that a plurality of test terminals provided in each of at least two different types of display devices are arranged with partially or completely the same pattern.
(2) In the manufacturing method according to (1), the circuit substrate includes a first test element group including at least two test elements for evaluating different characteristics from each other, the first test element group being connected to at least one of a plurality of first test terminals, and the plurality of first test terminals being included in the plurality of test terminals arranged with the common pattern.
(3) In the manufacturing method according to (2), the circuit substrate further includes a second test element group including at least two additional test elements for evaluating different characteristics from each other, the second test element group being connected to at least one of a plurality of second test terminals arranged with the same pattern as that of the plurality of first test terminals, and in the measuring step, the step of making the common probe in contact with the at least one of the plurality of first test terminals simultaneously is conducted independently of the step of making the common probe in contact with the at least one of the plurality of second test terminals simultaneously.
(4) In the manufacturing method according to (2), the at least two test elements include a resistance test element and a capacitance
Fujikawa Takashi
Kataoka Yoshiharu
Matsumoto Hitoshi
Nixon & Vanderhye P.C.
Pert Evan
Sharp Kabushiki Kaisha
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