Electrical characterization of flexible hafnium oxide capacitors on deformable softening polymer substrate

Abstract In this work, we investigate the electrical performance and compatibility of low-temperature hafnium oxide (HfO2) thin-film capacitors on a novel softening polymer substrate. Metal-insulator-metal HfO2 capacitors were fabricated using HfO2 as the dielectric material, deposited at 100 °C by atomic layer deposition (ALD), and gold as the top and bottom contacts. The HfO2 capacitors were fabricated on silicon and on softening polymer substrates with a dielectric thickness of 50, 40, 30, and 20 nm. The electrical performance of the MIM capacitors was measured and compared to determine the quality and compatibility of the low-temperature HfO2 deposition with the silicon and polymer substrate. The dielectric constant varied from 12 to 17 as the HfO2 thickness increased from 20 to 50 nm. Moreover, the capacitance density and dielectric constant of the capacitors on the polymer substrate differed by 3.9% ± 2% and 3.4% ± 2% with respect to the silicon substrate. The polymer substrate devices also have a higher leakage current, which suggests a higher number of defects in the dielectric film relative to Si substrates. Finally, the devices on the polymer substrate were subjected to bending cycles (up to 105 cycles) with a 5 mm bending radius to evaluate the resilience of the HfO2 capacitors against mechanical stress. The results show that the fabrication of the HfO2 thin-film capacitors on the softening polymer substrate is achievable with high stability and mechanical resilience. Overall, this research could assist the production of flexible biomedical devices on softening polymer substrates.