Development of thick film, CMOS compatible planar millimetre-wave antenna for antennas in package applications

Abstract

In this work, PI2611 polyimide is proposed as the dielectric layer to be able to integrate 60 GHz antennas into RF-chips. For this work, six layers were deposited on a silicon wafer using a multiple spin-coating process that included two final hard-bakes. The spin-coating process, however, can be repeated to obtain the desired thickness, thus eliminating the technological restriction existing in materials with different a coefficient of thermal expansion than that of silicon, where only two or three soft bakes and one hard-bake processes are allowed, restricting the final thickness to a few microns. The film was characterized using a profilometer (force 2 mg and resolution 0.5 µm), showing excellent planarity and stability for one cured-layer. The film was also used to fabricate a coplanar waveguide antenna for the 60 GHz band. The antenna was designed using a finite element 3D full-wave electromagnetic solver, and the measurements were performed with a Vector Network Analyser and RF-probes over a wide frequency range (between 20---67 GHz). A very good agreement between the simulated and experimental data validates the design and manufacturing methodologies.