Germanium (Ge) has gained great attention not only for future nanoelectronics but for back-end of line (BEOL) compatible monolithic three-dimensional (M3D) integration recently. For high performance and low power devices, various high-k oxide/Ge gate stacks including ferroelectric oxides have been investigated. Here, we demonstrate atomic layer deposited (ALD) polycrystalline (p-) HfO2/GeOX/Ge stack with an amorphous (a-) HfO2 capping layer. The consecutively deposited a-HfO2 capping layer improves hysteretic behaviors (ΔV) and interface state density (Dit) of the p-HfO2/GeOX/Ge stack. Furthermore, leakage current density (J) is significantly reduced (× 100) by passivating leakage paths through grain boundaries of p-HfO2. The proposed HfO2 layer with the graded crystallinity suggests possible high-k/Ge stacks for further optimized Ge MOS structures.
The EDA tool was supported by the IC Design Education Center (IDEC), South Korea.This work was supported in part by the Industrial Strategic Technology Development Program under Grant 20000300; and in part by the National Research and Development Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT under Grant 2020M3F3A2A01082593
