Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
2001-11-30
2004-10-26
Zarabian, Amir (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C345S098000, C359S016000
Reexamination Certificate
active
06809390
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a semiconductor chip mounting substrate bearing a semiconductor chip thereon. The present invention also relates to an electrooptical device that presents images using an electrooptical material such as a liquid crystal or an electroluminescent material, a liquid-crystal device that presents images by controlling the orientation of the liquid crystal to modulate light, an electroluminescent device that presents images using an organic electroluminescent element, and electronic equipment incorporating the electrooptical device.
2. Description of the Related Art
Electrooptical devices such a liquid-crystal device or an electroluminescent device (hereinafter referred to as an EL device) are widely used as a display unit in electronic equipment such as a mobile computer, a mobile telephone, and a video camera.
The liquid-crystal device with a liquid crystal as an electrooptical material sandwiched between a pair of electrodes controls the orientation of the liquid crystal by controlling a voltage applied to the electrodes, modulating a light beam transmitted through the liquid crystal, and thereby displaying an image such as characters and numerals.
The EL device with an EL light emission layer as an electrooptical material sandwiched between a pair of electrodes controls a voltage applied to these electrodes, thereby controlling a current fed to the EL light emission layer. The light emitted by the light emission layer is thus controlled, displaying an image such as characters and numerals.
In the liquid-crystal device or the EL device, electrodes for sandwiching the liquid crystal or the EL light emission layer are formed on one or a plurality of substrates. For example, the liquid-crystal device includes a pair of substrates facing each other having respective electrodes. On the other hand, the EL device includes, on the surface of one substrate, a pair of electrodes having an EL emission layer sandwiched therebetween. These electrooptical devices have a plurality of electrodes within an effective display area of the substrate, and extension lines extending from the plurality of electrodes, and metal lines, different from the extension lines, are arranged outside the effective display area. The electrodes formed within the effective display area are manufactured of oxides such as ITO, or a metal such as an APC alloy or Cr. When the electrodes are manufactured of a metal, the extension lines extending therefrom are also a metal wire.
For example, the metal lines, different from the extension lines, extending beyond the effective display area, may be used in a circuit board, such as a COG (Chip On Glass) board, on which a semiconductor chip is directly mounted. The metal lines in this case are connected to input terminals of the semiconductor chip, such as input bumps of the semiconductor chip, and connected to an FPC (Flexible Printed Circuit) leading to an external circuit.
It is known that the liquid-crystal device and the EL device employ an electrically conductive oxide such as ITO (Indium Tin Oxide) as a material for electrodes on the substrate, and a metal such as APC or Cr as a material for a metal line formed on the substrate. The APC is an alloy manufactured of Ag (silver), Pd (palladium), and Cu (copper).
The ITO has been widely used as a material for electrodes, etc. The ITO has a high electrical resistivity. If an ITO line is routed for a long path on a substrate, a resulting resistance becomes high, and a driving circuit cannot work normally. Contemplated as a promising material are low electrical resistivity metal such as APC or Cr. For example, resistance of ITO per unit area is 15 ohms, while resistance of Cr per unit area is 1.5 ohms and resistance of APC per unit area is 0.1 ohm. If a wiring pattern is manufactured of such a low resistivity metallic material on a substrate, a wiring pattern having a long length has advantageously a low resistance.
Fabricating a wiring pattern on a substrate of a metal such as APC or Cr advantageously lowers electrical resistance thereof. On the other hand, the use of metals present a new problem. The metal line is subject to corrosion. Due to migration, namely, the transfer of atoms damages the metal line, and the quality of wiring cannot be maintained.
The inventors of the present invention have conducted a variety of experiments in an attempt to resolve the problem of metallic corrosion or migration, and have reached the following conclusion. When a plurality of metal wirings is arranged side by side on a substrate, a potential difference may take place between adjacent wirings. In other words, a relationship of an anode and a cathode is established between the adjacent wirings, and a metallic component of the anode, for example, Ag is considered to dissolve.
In view of the above problem relating to the conventional wiring substrate, the present invention has been developed. It is an object of the present invention to prevent corrosion or migration from taking place in a metal wiring even when a wiring pattern is formed of a low electrical resistivity metallic material.
SUMMARY OF THE INVENTION
(1) To achieve the above object, a semiconductor chip mounting substrate of the present invention having a semiconductor chip mounted thereon, includes a power source line for supplying a supply voltage potential to the semiconductor chip, a ground line for supplying a ground voltage potential to the semiconductor chip, an output line to which an output signal from the semiconductor chip is supplied, and an insulator layer for covering the output line, wherein the insulator layer is formed clear of an area between the power source line and the ground line.
The lines formed on the substrate are typically divided into lines routed between an electrode and a driving element and lines routed between an external circuit board and the driving element. Migration mainly takes place in the line routed between the external circuit board and the driving element. The lines routed between the external circuit board and the driving element include power source supply voltage lines such as a power source line and a ground line, a data line for transferring a data signal, and a control signal for controlling drivers, etc.
The inventors have studied the problems, and have found that corrosion and migration take place at almost the same locations, particularly in the power source supply voltage lines. In contrast, the signal lines are almost free from migration. In other words, migration occurs in the power source supply voltage lines which present a large potential difference between adjacent lines.
According the observation of the inventors, the generation of migration is largely dependent on an insulator layer covering the lines. Specifically, the line is produced by forming a metal layer and then by patterning the metal layer. To pattern the metal layer, a photoresist is deposited on the metal layer, and etching is further performed. In this process, the surface of the line is inevitably contaminated. Although the substrate is cleaned after the formation of the line, contamination may occasionally not be fully removed.
If an insulator layer is deposited on the line with the surface thereof contaminated, the insulator layer contains the contamination with no escape path left. When the line is now supplied with a voltage potential, migration tends to occur more easily between adjacent lines in the power supply voltage system than in other areas because the potential difference between the adjacent lines, namely, the magnitude of electric field is large there. When the line is contaminated, contamination is encapsulated by the insulator layer. The application of voltage fully establishes a condition under which migration easily occurs.
In accordance with the present invention, the insulator layer is formed clear of the area between the power source line and the ground line. In other words, no insulator layer is arranged between the power source line and th
Makino Naoki
Toda Takatomo
Harness & Dickey & Pierce P.L.C.
Rose Kiesha
Seiko Epson Corporation
Zarabian Amir
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