Electrical properties and thermal stability in stack structure of HfO2/Al2O3/InSb by atomic layer deposition

We report on changes in the electrical properties and thermal stability of 5nm HfO2 grown on Al2O3-passivated InSb by atomic layer deposition (ALD). The deposited HfO2 on InSb at a temperature of 200 °C was in an amorphous... [ view full abstract ]

We report on changes in the electrical properties and thermal stability of 5nm HfO2 grown on Al2O3-passivated InSb by atomic layer deposition (ALD). The deposited HfO2 on InSb at a temperature of 200 °C was in an amorphous phase with low interfacial defect states. During post deposition annealing (PDA) at 400 °C, the In-Sb bonding was dissociated and diffused through HfO2. X-ray photoelectron spectroscopy (XPS) data indicated the diffusion of In atoms from the InSb substrate into the HfO2 during the PDA at 400 °C. This process generated In-O and Sb-O bonding on HfO2 surface, which degraded capacitance equivalent thickness (CET). We confirmed the generation of In-O and Sb-O bonding by using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The change in the defect states resulted from the diffused In and Sb was also investigated by C-V measurement. 1nm-thick Al2O3 as a passivation layer on InSb substrate reduced the diffusion of In atoms and improved thermal stability. In addition, stress induced leakage current (SILC) data showed that gate leakage current was reduced by the passivation layer. Using the C-V measurement, the change in border traps was investigated: border trap density after the annealing treatment was increased, compared to that of as-grown sample, which is caused by In atoms located between Al2O3 and InSb. As a result, even though border trap density was increased by the Al2O3 layer on InSb substrate, the thermal stability at the interfacial region and gate leakage current could be successfully accomplished by the Al2O3 layer.