Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-05-22
2003-09-30
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S679000
Reexamination Certificate
active
06627544
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a metal film pattern and a manufacturing method thereof. A wiring substrate having the metal film pattern of the present invention formed thereon is utilized in various applications such as flat panel displays (e.g., liquid crystal display devices (LCDs), plasma display devices (PDPs), electrochromic display devices (ECDs) and electroluminescent display devices (ELDs)), two-dimensional image detectors, and various electric circuit boards. The metal film pattern of the present invention can also be used as a photomask.
2. Description of the Background Art
In flat panel displays including liquid crystal display devices (LCDs), a display material such as a liquid crystal material or discharge gas is interposed between a pair of substrates. The display material is driven by applying a voltage thereto. Electric wirings of a conductive material are formed on at least one of the substrates.
For example, in the active-matrix display, gate electrodes and data electrodes are arranged in a matrix on one of a pair of substrates having a display material interposed therebetween (i.e., an active matrix substrate). A thin film transistor (TFT) and a picture element electrode are provided at every intersection of the gate electrodes and the data electrodes. The gate electrodes and the data electrodes are normally formed from a metal material such as Ta, Al or Mo by using a vacuum film-formation method such as sputtering method.
The size of a mother substrate used in a manufacturing process of such a flat panel display is ever increasing, and formation of metal wirings (electric wirings) on a large-area substrate on the order of meters is increasingly demanded. However, forming metal wirings on such a large-area substrate by a conventional vacuum film-formation method is problematic in the following points: it is difficult to form metal films having a uniform thickness and quality; and a huge vapor film-formation apparatus and thus an enormous amount of investment in plant and equipment are required.
Moreover, a vapor film-formation apparatus such as a sputtering apparatus and CVD (Chemical Vapor Deposition) apparatus requires a large amount of electric power such as that for driving a vacuum pump, heating a substrate and generating plasma. Of course, energy consumption of the manufacturing apparatus is also increased with increase in size thereof.
Moreover, a metal wiring pattern must be formed by forming a metal film over the whole surface of a substrate by using a vapor film-formation apparatus and then etching away the most part of the metal film (i.e., unnecessary part of the metal film). This causes waste of the metal material (i.e., low material utilization rate). In particular, reduction in energy consumption in the manufacturing process and suppression of the waste of material resources (effective utilization of material resources) are recently strongly demanded due to environmental concerns.
One way to solve the above problems caused by the vacuum film-formation process is to form metal wirings by using a wet film-formation technology instead of a vacuum film-formation method. For example, Japanese Laid-Open Publication No. 4-232922 discloses a method for forming a metal film of Cu, Ni or the like on an underlying film by using a plating technology. In this method, a transparent electrode of ITO (Indium Tin Oxide) or the like is used as the underlying film. This method does not use a vacuum film-formation apparatus to form the metal film. This suppresses increase in investment for manufacturing facility and increase in energy consumption in the manufacturing process. Moreover, the metal film can be selectively formed only on the ITO film by a plating method. This suppresses the waste of the metal material.
In this case, the metal film is formed by the plating technology that does not use a vacuum film-formation apparatus. However, the ITO film serving as an underlying film for the metal film is still formed by a dry vacuum film-formation technology such as a sputtering method and vapor deposition method. Accordingly, the above problems involved in the vacuum film-formation process cannot completely be solved.
Japanese Laid-Open Publication No. 2001-032086 discloses a method for forming even an underlying oxide film (e.g., ITO film), i.e., an underlying film for the metal film, by using a wet film-formation technology. In other words, this publication discloses a method for forming both an oxide film serving as an underlying pattern and various metal films selectively formed thereon by a wet film-formation process. In this method, the underlying pattern (oxide film) is formed by using a sol-gel method, one of the wet film-formation technologies, and a metal film (e.g., a laminated film of Ni, Au and Cu) is selectively formed only on the oxide film by using a wet plating method.
The sol-gel method is a method for producing an oxide solid by producing a sol-gel solution by using an organic or inorganic compound of a metal and a solvent, applying the sol-gel solution to a substrate, promoting hydrolysis and polycondensation reaction of the compound on the substrate so as to solidify a sol into a gel, and heating the gel. The use of the sol-gel method enables the oxide film to be formed by merely applying a sol-gel solution to a substrate such as glass and baking the resultant substrate. This eliminates the need to use a vacuum film-formation apparatus as in the conventional example.
The use of a method in which a sol-gel solution is blended with a photosensitive (photopolymerizable or photodegradable) material in advance or a method utilizing a photolysis reaction of a gel film chemically modified with a chelating agent enables patterning of a sol-gel applied film by a photolithography technology. By optimizing the composition of a sol-gel solution and the conditions for application and baking processes facilitates formation of a thin oxide film having a thickness of 0.1 &mgr;m or less and even a fine pattern having a line and space (L/S) of 10 &mgr;m or less. Therefore, an oxide film formed by the sol-gel method is optimal as an underlying film for a metal wiring pattern.
Note that, in the specification, the following method for forming an oxide film also falls within the category of the sol-gel method in a broad sense: in order to improve the stability of a sol in the atmosphere, a metal chelate complex solution with its hydrolysis and polycondensation reaction suppressed is used as a solution to be applied to the substrate, and an oxide film is formed by thermal decomposition of the metal chelate complex film.
The inventors formed metal wirings by an electroless nickel (Ni) plating method on an oxide film formed by a sol-gel method. In this experimentation, the inventors found that the metal film is deposited outside the pattern depending on the composition of the electroless nickel plating solution and such deposition outside the pattern is remarkable in a fine line pattern portion, and particularly in a portion having a line-space of 10 &mgr;m or less. When such deposition outside the pattern occurs in fine wirings, the insulating property between patterns is degraded, and in a worse case, short-circuiting occurs. Accordingly, deposition outside the pattern must be eliminated as much as possible upon forming the metal wirings.
It is an object of the present invention to prevent deposition of a metal film outside the pattern from occurring in a fine line pattern portion, and particularly in a portion having a line-space of 10 &mgr;m or less, when a metal film pattern is formed by an electroless plating method.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a method for manufacturing a metal film pattern includes the steps of: forming an oxide film having a prescribed pattern feature on a substrate by a wet film-formation technology; and forming a metal film on the oxide film by an electroless plating method. The electroless plating method is conducted in the presence of
Chikama Yoshimasa
Hashimoto Takaharu
Ishikawa Masaaki
Izumi Yoshihiro
Kawashima Satoshi
Gurley Lynne
Niebling John F.
Nixon & Vanderhye P.C.
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