Cryogenic Behavior of High-Permittivity Gate Dielectrics: The Impact of the Atomic Layer Deposition Temperature and the Lithographic Patterning Method

TL;DR

This study investigates how ALD temperature and lithographic patterning methods affect the cryogenic performance of high-k dielectrics, revealing significant dependencies for HfO2 and minimal impact on Al2O3.

Contribution

It provides new insights into the cryogenic behavior of high-k dielectrics, especially HfO2, and explores the effects of fabrication parameters on their electrical properties at 3 K.

Findings

HfO2 performance strongly depends on ALD temperature at cryogenic temperatures.

Al2O3 shows negligible change with ALD temperature from 300 K to 3 K.

Cryogenic permittivity of HfO2 and Al2O3 reduces by approximately 9% and 14%, respectively.

Abstract

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 we extrapolated relative permittivity (k) and dielectric strength (E_BD) from AC (100 Hz to 100 kHz) and DC measurements on metal-insulator-metal capacitors. Our findings reveal a strong dependence of HfO2 cryogenic performance on the ALD growth temperature, while the latter shows a negligible impact on Al2O3. We estimated a ~9 % and ~14 % reduction of the relative permittivity of HfO2 and Al2O3, respectively, from 300 K to 3 K. Additionally, we designed and fabricated Al2O3/HfO2 bilayers and we 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.