Bendable 190-GHz Transmitter on 20-μm Ultra-Thin SiGe BiCMOS

Abstract

This research work presents the fabrication and characterization of ultra-thin fully integrated transmitter circuits. By moving bendable technology into the 190-GHz band, it is possible to implement complete transmitter systems or sensor nodes, including on-chip antennas, on a single chip without the need for surrounding circuits, thus increasing system performance and reducing cost. To fabricate such thin chips, a standard 700-<inline-formula> <tex-math notation="LaTeX">$\mathrm {\mu }\text{m}$ </tex-math></inline-formula> fully processed SiGe BiCMOS wafer was thinned to a thickness of only 20 <inline-formula> <tex-math notation="LaTeX">$\mathrm {\mu }\text{m}$ </tex-math></inline-formula> making the silicon bendable. The transmitter, which consists of a voltage-controlled oscillator, a power amplifier, and an on-chip antenna, was characterized by comparing thinned and standard thickness samples. Therefore, a maximum relative deviation of the oscillator frequency tuning of less than 2&#x0025; was found. The oscillation frequency of the chip is measured in a bent state, resulting in a maximum relative deviation for bend radii of up to 4 mm of only 1&#x0025;. Considering a maximum output power deviation of 4.6 dB, the presented approach proves to be feasible for the design of flexible high-performance integrated systems. This enables novel applications in the field of medicine, wearable electronics, and the Internet of Things.