The Reflectivity enhancement of Ni/Ag/(Ti or Mo)/Au Ohmic Contact for Flip-Chip Light-Emitting Diode Applications

The proposed multilayer structures Ni/Ag/M/Au, with blocking metal (M) of Ti and Mo, to form both ohmic and reflective contact for flip chip light emitting diode (FCLED) application, are fabricated. During the annealing process of conventional three-layer Ni/Ag/Au contacts, serious Au intermixing with Ag and Ni was found to result in poor reflectance (63% at the wavelength of 465 nm). It is found that the inserted (between Ni/Ag and Au) diffusion barrier (Ti or Mo) can block Au inter diffusion effectively and hence improves the correspondent FCLED reflectivity (as high as 93%).