Micromachined Millimeter- and Submillimeter-wave Circuits for Test and Integration

The terahertz spectrum is critical to a wide range of scientific applications, from radio astronomy to remote sensing. However, due to the cost, size and weight of terahertz systems, the terahertz frequency range remains one of the least explored and utilized regions of the electromagnetic spectrum. To reduce the size, weight and cost of terahertz components, one of the solutions is to fabricate high density integrated circuits.

Although progress has been made in the development of submillimeter-wave monolithic integrated circuits, the evaluation of these circuits still relies on test fixtures, which makes testing expensive and time consuming. A micromachined on-wafer probe covering frequencies 500-750 GHz has been demonstrated in this work to simplify submillimeter-wave integrated circuits testing.

This work also presents the design, simulation and measurement of a vertical RF interconnect with mechanical fit for three-dimensional heterogeneous integration, which is one of the major technologies for system miniaturization. The mechanical fit is a flip-chip strategy employing SU-8, an ultra-thick photoresist, to realize interlocking structures that prevent misalignment during assembly and increase the reliability of the interconnects. To determine the electromagnetic characteristics, such as insertion loss and the coupling between face-to-face chips, different test structures were fabricated and measured.