Copper Deposition and Patterning for Glass Substrate Manufacture

Glass is a potential substrate material for the manufacture of substrates for high density electrical and optical interconnect. However, in order to realize such substrates, metallization is required to form conductive tracks and pads. In this work, electroless copper was used due to its relatively low cost, fast speed and potential for high volume production. Silanisation of the glass surfaces with (3-aminopropyl) trimethoxysilane (APTS) was used to provide a surface-coupled layer of functional molecules to assist in the adhesion of Pd/Sn catalyst and the subsequent copper deposition. The composition and microstructure of the modified glass surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Tape peel testing was used to qualitatively assess the adhesion of the copper to the smooth glass surface. For layers less than 150 nm thick, adhesion was good, but thicker coatings tended to peel away easily. Preliminary analysis of the peeled surfaces indicated that failure occurred at the interface between the copper and the catalyst. As an alternative approach for improving adhesion, laser machining was used to roughen the glass and direct the deposition of electroless copper, such that circuit patterns with good adhesion were formed.