1. Field of the Invention
The present invention relates to a preparation method for an electroconductive patterned copper layer such as a copper wiring layer of circuit boards or semiconductor devices or a copper electrode layer of various displays, and a patterned copper layer formed by the method. More particularly, the present invention relates to a preparation method of a patterned copper layer with electric conductivity by firing a copper-based particle patterned layer in the air, and a patterned copper layer formed by the method.
2. Description of the Related Art
Circuit boards, semiconductor devices, and various displays have a patterned layer such as a wiring layer or an electrode layer, which is made of metal such as copper, nickel or silver. In particular, a patterned layer using copper is widely used due to good electric conductivity and low price.
Particularly, copper particles and copper oxide particles such as cuprous oxide may be produced with small diameter in a several nanometer or several micrometer level such that they may form a fine pattern, so they are useful in forming an electroconductive patterned copper layer.
According to conventional methods for forming an electroconductive patterned copper layer using copper-based particles, a copper-based particle dispersion solution obtained by dispersing copper-based particles in a solvent is printed on a substrate surface or filled in through holes of the substrate to form a copper-based particle patterned layer, and then the layer is thermally treated at a high temperature under the inert gas circumstance such as a nitrogen gas environment for firing. Accordingly, among the copper-based particles contained in the copper-based particle patterned layer, copper oxides are reduced into copper and thus connected with each other, and organic substances included in the paste are removed, so an electroconductive patterned copper layer is formed (see Japanese Laid-open Patent Publication No. 2006-93003).
According to such a method for forming a common electroconductive copper-based, it is possible to give a patterned copper layer with good electric conductivity. However, the firing process should be executed under an inert gas circumstance in the industrial aspect, there is needed a device for supplying an inert gas, and also it is required to perform thermal treatment in a space kept with the inert gas atmosphere, which however gives more burdens in aspect of costs.
If the above copper-based particle patterned layer is thermally treated and fired in a atmospheric circumstance, not in an inert gas circumstance, an oxidation reaction occurs to the copper due to the oxygen in the air during the thermal treatment process, which results in bad quality of electric conductivity of the patterned copper layer.