Low-temperature bonding of Cu on Si3N4 substrate by using Ti/Cu thin films

A low-temperature bonding method of Si3N4/Si3N4 homostructure and Si3N4/Cu heterostructure was developed in this work. The flawless interfaces were obtained by sputtered Ti/Cu thin films after bonding at 250 °C for 30 min under a uniaxial pressure of 20 MPa. The Ti film is able to improve the adhesion of the Cu film to Si3N4 substrate, and the low-temperature bonding was achieved in view of high diffusion rates of Cu nanocrystalline film with (1 1 1) crystal plane. This proof-of-concept study on the low-temperature bonding of Si3N4 ceramic to Cu is expected to address residual stress caused by ordinary active metal brazing (AMB) method, which provides insights for the further heterogeneous integrations of ceramics to metals.