Investigation of BEoL integrated ferroelectric thin-film HfO2 for mmWave varactor applications

In this paper, we demonstrate Back-End-of-Line (BEoL) integrated thin-film varactors based on ferroelectric hafnium zirconium oxide. We furthermore show the implementation of such novel metal-ferroelectric-metal (MFM) thin-film varactors in a passive delay-line phase shifter at millimeter wave frequencies. Upon the frequencies up to 67 GHz and a small voltage range of -3V to 2V, the device has demonstrated the phase shift of 43.5° at 45 GHz with an insertion loss (IL) of 14 dB, and 112 ° at 60 GHz with an IL of -41.3 dB. The device area is 0.512 mm
²
excluding the pads. Its exceptional CMOS compatibility, making it suitable for all major CMOS and BiCMOS technologies, and its low-voltage operation make it a promising candidate for a wide range of microwave and millimeter-wave applications.