Low-Voltage Phase Shifters Based on HfxZr1-xO2 Ferroelectrics Integrated with Phased Antenna Arrays

In this paper, we present the design, fabrication and microwave experimental characterisation of a ferroelectric phase shifter, which is integrated with a 2-element antenna array to achieve beam-steering capabilities at very low voltages of ±1 V. The phase shifter consists of an interdigitated metallic capacitor deposited on a Zr-doped ferroelectric hafnium dioxide (Hf
_x
Zr
_1-x
O
₂
) thin film, directly grown on high-resistivity Silicon (HR Si). The phase shifter shows a maximum phase shift of 53.74° at 2.55 GHz, sweeping the DC voltage between -1 V and +1 V. The miniaturised phased array is in the form of two gold patch antennas, phase shifters and additional circuitry, all integrated on HfxZr
_1-x
O
₂
/HR Si 4-inch wafer. The radiation beam at 2.55 GHz is steered with 25° when the 7-nm-thick ferroelectric is biased with ±1 V. These new microwave devices represent a step forward in the realisation of low-voltage tunable microwave components for the upcoming 5G technology.