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.
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
