Cryogenic behavior of high-permittivity gate dielectrics: The impact of atomic layer deposition temperature and the lithographic patterning method

Dielectrics featuring a high relative permittivity, i.e., high-k dielectrics, have become the standard insulators in gate architectures, enhancing the electrical performance of both room temperature and cryogenic electronics. This study delves into the cryogenic (3 K) performance of high-k dielectrics commonly used as gate insulators. We fabricated Al2O3 and HfO2 layers via atomic layer deposition (ALD) and extrapolated relative permittivity (k) and dielectric strength (EBD) from AC (100 Hz–100 kHz) and DC measurements on metal–insulator–metal capacitors. Our findings reveal a strong dependence of HfO2 cryogenic performance on ALD growth temperature, while the latter shows a negligible impact on Al2O3. We estimated ∼9% and ∼14% reductions in the relative permittivities of HfO2 and Al2O3, respectively, at temperatures from 300 to 3 K. Additionally, we designed and fabricated Al2O3/HfO2 bilayers and checked their properties at cryogenic temperatures. The study also investigates the impact of the patterning method, namely, UV or electron-beam lithography (acceleration voltage of 10, 20, or 30 kV), on the high-k dielectric properties.