Heterogeneous Chip Integration Process for Flexible Wireless Microsystem Application

This paper presents a low-cost heterogeneous integration technology combining the previously developed bump less radio-frequency (RF) system-on-a-package scheme with a special surface cleaning process to assemble a complementary metal-oxide-semiconductor chip with an organic substrate (SU-8/ polydimethylsiloxane) by low-temperature Au-Au thermocompressive bonds (<; 200°C) for flexible wireless microsystem fabrication. The RF performance of -15 dB return loss and -0.25 dB insertion loss at 40 GHz and above 6 MPa bonding strength of a microstrip-to-coplanar-waveguide interconnect transition between the chip and the substrate make the technology practical for flexible wireless microsystem integration.