Semiconductor device manufacturing: process – Making device array and selectively interconnecting
Reexamination Certificate
2002-05-02
2004-04-13
Thompson, Craig A. (Department: 2813)
Semiconductor device manufacturing: process
Making device array and selectively interconnecting
Reexamination Certificate
active
06720211
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for fabricating electric interconnections to be used for electronic circuit boards of electric equipment such as a flat panel display or a two-dimensional image detector, further relates to an interconnection substrate applicable to a variety of electronic devices, relates to display devices such as a liquid crystal display (LCD), a plasma display (PDP), an electrochromic display (ECD), an electroluminescent display (ELD) and relates to an image detector using light or radial rays.
Conventionally, in a flat panel display represented by the liquid crystal display, display material such as liquid crystal or electric discharge gas is normally held between a pair of substrates, and a voltage is applied to this display material. In this stage, electric interconnections made of conductive material are provided at least on one substrate.
For example, in the case of an active matrix drive type display, gate electrodes and data electrodes are arranged in a matrix form on one substrate (active matrix substrate) of a pair of substrates that hold the display material between them, and a thin film transistor (TFT) and a pixel electrode are arranged at each intersection. These gate electrodes and data electrodes are normally made of a metal material such as Ta, Al or Mo and formed into a film by a dry film forming method such as a sputtering method.
There has also been developed a flat panel type two-dimensional image detector obtained by combining an active matrix substrate having a construction similar to that of the aforementioned active matrix drive type display with a photodetector element or an X-ray detecting element. The details of the two-dimensional image detector are disclosed in the reference documents of “L. S Jeromin, et al., “Application of a-Si Active-Matrix Technology in X-Ray Detector Panel”, SID 97 DIGEST, p.91-94, 1997”, “Japanese Patent Laid-Open Publication No. HEI 6-342098” and others.
If it is tried to increase the area and improve the definition of the flat panel display or the two-dimensional image detector of the above kind, then the resistance and parasitic capacitance of the electric interconnections increase as the drive frequency increases, and accordingly, the delay of the drive signal emerges as a serious problem.
Therefore, in order to solve the problem of this drive signal delay, it is tried to use low electric resistance Cu (bulk resistivity is 1.7 &mgr;&OHgr;·cm) as an interconnection material instead of the conventional interconnection materials of Al (bulk resistivity is 2.7 &mgr;&OHgr;·cm), &agr;-Ta (bulk resistivity is 13.1 &mgr;&OHgr;·cm) and Mo (bulk resistivity is 5.8 &mgr;&OHgr;·cm). There is a disclosure of the examination of a TFT liquid crystal display (TFT-LCD) employing Cu as a gate electrode material in, for example, the reference of “Low Resistance Copper Address Line for TFT-LCD” (Japan Display '89 p.498-501). This reference document states clearly the necessity for improving the adhesion by interposing a metal film of Ta or the like on the groundwork since the Cu film formed by the sputtering method has poor adhesion to the groundwork glass substrate.
However, in the case of the interconnection structure in which a metal film of Ta or the like is provided as an interposition on the above-mentioned groundwork, the Cu film and the groundwork metal film of Ta or the like need individual dry film forming processes and etching processes, and this disadvantageously causes an increased number of processes and cost increase.
In view of the above, the prior art reference of Japanese Patent Laid-Open Publication No. HEI 4-232922 proposes electric interconnection fabricating method for using a transparent electrode made of indium-tin-oxide (ITO: tin-added indium oxide) or the like as a groundwork film and forming by a technique of plating the surface of the groundwork film with a metal film of Cu or the like. According to this technique, there is clearly stated the effect of allowing Cu interconnections to be efficiently formed even in a large area since the plating metal can be formed as a film selectively on the ITO film and therefore the patterning process is necessary for only the ITO film of the transparent electrode. There is also stated a structure for interposing a metal film of Ni or the like having a good adhesion property between ITO and Cu.
There has also been proposed electric interconnection fabricating method for forming a metal film of Ni, Au, Cu or the like on a patterned ITO film by a plating technique for the various purposes of reducing the processes of the active matrix substrate, reducing the resistance of the transparent electrode of a simple matrix type liquid crystal display device, increasing the solder wettability on the ITO film and so on besides the electric interconnection fabricating method described in the aforementioned prior art reference of Japanese Patent Laid-Open Publication No. HEI 4-232922 (refer to, for example, the prior art reference documents of Japanese Patent Laid-Open Publication No. HEI 2-83533, Japanese Patent Laid-Open Publication No. HEI 2-223924, Japanese Patent Laid-Open Publication No. SHO 62-288883 and Japanese Patent Laid-Open Publication No. HEI 1-96383).
However, in the case of the electric interconnection fabricating method using ITO for the groundwork, the metal film is formed by the plating technique using no vacuum film forming apparatus. However, the ITO film that becomes the groundwork of the metal film is formed still by a vacuum film forming apparatus of the sputtering method or the vacuum deposition method. This leads to the problem that a sufficient cost reduction effect cannot be obtained and the method cannot easily cope with a large-area substrate.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an electric interconnection fabricating method, an interconnection substrate, a display device and an image detector, which is able to be fabricated at low cost and to easily cope with a large-area substrate using no vacuum film forming apparatus.
In order to achieve the aforementioned object, the present invention provides an electric interconnection fabricating method comprising: an oxide film forming process for forming an oxide film on an insulating substrate by a first wet type film forming technique; and a metal film forming process for forming a metal film on the oxide film by a second wet type film forming technique.
According to the above invention, the electric interconnections having the laminate structure formed of the metal film and the oxide film can be obtained using no vacuum film forming apparatus, and the sufficient cost reduction effect can be obtained by comparison with the conventional electric interconnection fabricating method. The first and second wet type film forming techniques can easily cope with the large-area substrate since the first and second wet type film forming techniques can more easily form a large-area film than the vacuum film forming technique. The electric interconnections having a laminate structure formed of the metal film and the oxide film can be obtained without using any vacuum film forming apparatus. Therefore, electric interconnections can be easily formed on an insulating substrate (a polymer film, for example) or the like made of an organic material besides a glass substrate having excellent vacuum resistance and heat resistance. Furthermore, electric interconnections can be formed with high productivity according to a roll-to-roll system using a long film base material.
In one embodiment of the present invention, the electric interconnection fabricating method further comprises a patterning process for patterning the oxide film according to a specified shape between the oxide film forming process and the metal film forming process.
According to the above embodiment, the metal film formed through the metal film forming process can be selectively formed only on the oxide film patterned according to a specified shape through
Chikama Yoshimasa
Izumi Yoshihiro
Ochi Hisao
Conlin, Esq. David G.
Edwards & Angell LLP
Roos, Esq. Richard J.
Sharp Kabushiki Kaisha
Thompson Craig A.
LandOfFree
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