Photochemical patterning of low resistivity metals by amorphous $TiO_2$ layer

Abstract

A new metal patterning process was developed to reduce the number of chemical processing steps and to obtain fine patterns of 10 μm line width. Films of amorphous $TiO_2$ and water-soluble polyvinyl alcohol were used as photocatalytic layers. UV light of shorter than 365 nm was illuminated through photomask in order to form latent image which has an ability of reducing some noble metal like palladium and silver. Palladium and silver activators formed on the UV exposed area of photocatalyst could induce the formation of Ni, Cu and Ag by electroless plating. Electroless Ni plating resulted in the formation of high resolution and adhesive metal pattern to substrates whereas Cu and Ag direct electroless plating on photocatalyst did not provide the high conductivity metal pattern thicker than 0.3 μm. The subsequent selective deposition of Cu metal by electroless/ electro plating on patterned Ni could result in the formation of high resolution and conductive metal pattern depending on such factors as composition of plating solution and treatment conditions. It was established that high resolution metal patterns of low resistivity with good adhesion were formed only at a small process steps without using high cost materials and equipments. Selective growth of carbon nanotubes on the Ni patterns was carried out by plasma-enhanced chemical vapor deposition. It’s expected that this methods will have several benefits for fabricating the microelectronic devices, especially in the large size flat panel display.