A Reconfigurable Inductor Based on Vanadium Dioxide Insulator-to-Metal Transition

Abstract

This letter introduces a reconfigurable planar square-coil-shaped inductor exploiting as the tuning mechanism the insulator-to-metal transition (IMT) of a Vanadium Dioxide (VO2) switch placed in the inter-winding space in an unprecedented manner. The VO2 thin film barshaped switch is electrically connected to provide a temperature-selective current path that effectively shortcircuits a part of the inductor coil changing the inductance of the device. The inductor is fabricated on a high-resistivity Silicon substrate (HR-Si) using a CMOS compatible 2D planar low-cost technology (4 photolithography steps). The design, optimized to work in the 4 to 10 GHz range, provides measured inductances at 5 GHz of 2.1 nH at 20 °C and 1.35 nH at 100 °C with good stability in the entire frequency band (4-10 GHz) resulting in a reconfiguration ratio of 55 %. The quality factor (Q-factor) at 7 GHz is about 8 at 20 °C (OFF-state) and 3 at 100 °C (ON-state), outperforming tunable inductors employing VO2 with 2 orders of magnitude higher Q-factor and a smaller footprint. This represents an advancement for the state-of-the-art of 2D CMOS compatible inductors in the considered frequency range.

A Novel Reconfigurable CMOS Compatible Ka Band Bandstop Structure Using Split-Ring Resonators and Vanadium Dioxide (VO2) Phase Change Switches

“…show the conductivity of the VO 2 films in the on state (around one order of magnitude smaller than the ones reported on Sapphire, Cooper or Fr-4, see Table 1. but which are better than the ones reported in [12][13][14] for SiO 2 /Si based depositions. On the other hand the values for the insulating (off state conductivity) are more than twice higher than the reported ones in [12][13][14] (for samples 2-4) and thus more care has to be taken in the design for the off state too.…”

“…but which are better than the ones reported in [12][13][14] for SiO 2 /Si based depositions. On the other hand the values for the insulating (off state conductivity) are more than twice higher than the reported ones in [12][13][14] (for samples 2-4) and thus more care has to be taken in the design for the off state too. Starting from the uniplanar SRR [15] we have added four SRR in the slots at a same metal level with the central strip of a CPW line.…”

“…The IMT transition can be triggered thermally around 68 °C with increasing temperature while MIT can be achieved with decreasing temperature. VO 2 has been employed in several reconfigurable components and deposited as a thin film on sapphire [3][4][5][6][7], Si [6], on Alumina [8], cooper [9], Quartz [10], FR4 [11], SiO2/Si [12][13][14], among others exhibiting a huge but inconstant change in the conductivity levels between its insulating (off) and conductive (on) states of several orders of magnitude. Table 1.…”

“…presents various approximate conductivity levels reported within [3][4][5][6][7][8][9][10][11][12][13][14] for different VO 2 depositions of different thicknesses and employing different deposition techniques. It is worth mentioning that a large variety of these stated values are presumed based on similar configurations [3,4,7,11,13,14], measured for the exact depositions [5,6,9,12] while frequency dependent extracted [10] by de-embedding. Quartz 50< c on <200 c off >4*10 4 (100 0 C) [11] FR-4 4600 8*10 5 [12] SiO 2 /Si 10 2.3*10 4 [13] SiO 2 /Si 20 unreported [14] SiO 2 /Si unreported 3*10 4…”

“…It is worth mentioning that a large variety of these stated values are presumed based on similar configurations [3,4,7,11,13,14], measured for the exact depositions [5,6,9,12] while frequency dependent extracted [10] by de-embedding. Quartz 50< c on <200 c off >4*10 4 (100 0 C) [11] FR-4 4600 8*10 5 [12] SiO 2 /Si 10 2.3*10 4 [13] SiO 2 /Si 20 unreported [14] SiO 2 /Si unreported 3*10 4…”