Applied Physics Letters
Evidence of indium diffusion through high-k dielectric (Al2O3 and HfO2) films grown on InP (100) by atomic layer deposition is observed by angle resolved X-ray photoelectron spectroscopy and low energy ion scattering spectroscopy. The analysis establishes that In-out diffusion occurs and results in the formation of a POx rich interface.High mobility III-V channel materials are contenders to replace Si in semiconductor devices like metal oxide semiconductor filed effect transistors (MOSFETs) for the sub 22 nm technology node.1 Extensive research is being carried out to determine the validity of these III-V materials for use as the channel, in a variety of structures ranging from planar to 3D Fin-FETs.2,3 However, the improvement of interfacial quality between a high-k dielectric and these III-V materials is still a hurdle to overcome in order to achieve suitable electrical performance.4 Efforts have been made recently using InP as a barrier layer between InGaAs and the high-k dielectrics, which show improved electrical performance relative to devices with the high-k dielectrics directly in contact with the channel.5,6 Recently, however, Gu et al. reported that the interface between this InP barrier layer and high-k dielectrics impact the sub-threshold swing of the devices.7 The density of interface states (Dit) has been found to be strongly correlated to the In-P-oxides present at the interface based on a study investigating the impact of post deposition annealing (PDA) of HfO2 on InP at different temperatures.8 An et al. and Kang et al. have reported diffusion of In atoms and P-oxides through a thick (>6 nm) HfO2 layer on InP by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS).9–11 However, detailed analysis of this substrate elemental diffusion through other high-k dielectrics as well as interfacial chemistry upon annealing has not been reported.In this study, the diffusion behavior of the substrate elements in the HfO2/InP and Al2O3/InP systems is studied by angle resolved X-ray photoelectron spectroscopy (ARXPS) and low energy ion scattering spectroscopy (LEIS). In order to highlight the significance of In-diffusion and rule out the possibility of interfacial oxide regrowth due to air exposure,12 thick HfO2 (∼5.6 nm) and Al2O3 (∼5 nm) films on various of InP (100) samples are grown by atomic layer deposition (ALD).Four n-type InP (100) samples, cleaved from the same 50 mm single crystal wafer obtained from IQE Ltd., are used in this study, and the treatments are listed in Table I. Samples A and C are native oxide InP (100) degreased using sequential dips in acetone, methanol, and isopropyl alcohol for 1 min each, and samples B and D are initially degreased and then treated by 10% (NH4)2S at room temperature for 20 min.13 The (NH4)2S treatment is widely used to decrease the native oxide concentration and passivate the III-V semiconductor surfaces to reduce reoxidation prior to high-k dielectric deposition,7,13 and is used in this study to compare the relative thermal stability of native oxide and (NH4)2S treated surfaces.
H. Dong, W. Cabrera, R. Galatage, Santosh KC, B. Brennan, X. Qin, S. McDonnell, D. Zhernokletov, C. Hinkle, K. Cho, Y. Chabal, and R. Wallace. "Indium diffusion through high-k dielectrics in high-k/InP stacks" Applied Physics Letters (2013). https://doi.org/10.1063/1.4817932