We investigated the flat band voltage (VFB) modulation by insertion of lanthanum oxide (La2 O3) into hafnium oxide (HfO 2) gate dielectrics. The properties of La2 O3 / HfO2 nanolaminates were precisely modulated by controlling the position of La2 O3 layer at bottom, middle, or top using atomic layer deposition. When the La2 O3 layer was positioned closer to the interface (bottom), the reduction in VFB shift was more effective than the other two cases (middle and top). From our experimental results, we propose that the main mechanism of VFB modulation using La 2 O3 layer is dipole moment formation at an interfacial layer between high k gate dielectric and Si substrate.
Bibliographical noteFunding Information:
This work was supported by the Technology Innovation Program funded by the Ministry of Knowledge Economy (MKE, Korea, Grant No. 10030519). Also, this work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) and by Nano R&D program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science, and Technology (Grant Nos. 2009-0083749 and 2009-0082853). FIG. 1. Schematic drawings for three kinds of HfO 2 / La 2 O 3 laminate profiles (H/L, H/L/H, and L/H, respectively). FIG. 2. XPS spectra of the PE-ALD La 2 O 3 / HfO 2 nanolaminates: (a) O 1 s , (b) La 3 d 5 / 2 . FIG. 3. Electrical properties of MOS capacitors using the PE-ALD La 2 O 3 / HfO 2 nanolaminates as gate insulators after HTA processing at 700 ° C for 10 s in Ar atmosphere: (a) the C-V curves, (b) the interface state density ( D it ) , and leakage current density at −1 MV/cm. FIG. 4. Δ V FB for the three types of the PE-ALD La 2 O 3 / HfO 2 laminates and the La 2 O 3 after HTA processing at 700 ° C for 10 s in Ar atmosphere (standard sample: HfO 2 ). FIG. 5. Schematic drawings for the V FB modulation mechanism using the typical case of H/L/H sample: (a) diffusion of the La atoms from the inserted La 2 O 3 layer into the interfacial layer, (b) modulation of metal EWF from negative field by the interface dipole (Hf–O–La configuration).
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)