Abstract
Changes in the electrical properties and thermal stability of HfO2 grown on Al2O3-passivated InSb by atomic layer deposition (ALD) were investigated. 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, In–Sb bonding was dissociated and diffusion through HfO2 occurred. The diffusion of indium atoms from the InSb substrate into the HfO2 increased during PDA at 400 °C. Most of the diffused atoms reacted with oxygen in the overall HfO2 layer, which degraded the capacitance equivalent thickness (CET). However, since a 1-nm-thick Al2O3 passivation layer on the InSb substrate effectively reduced the diffusion of indium atoms, we could significantly improve the thermal stability of the capacitor. In addition, we could dramatically reduce the gate leakage current by the Al2O3 passivation layer. Even if the border traps measured by C–V data were slightly larger than those of the as-grown sample without the passivation layer, the interface trap density was reduced by the Al2O3 passivation layer. As a result, the passivation layer effectively improved the thermal stability of the capacitor and reduced the interface trap density, compared with the sample without the passivation layer.
Highlights
At 400 °C, In–Sb bonding was dissociated and diffusion through HfO2 occurred
An interfacial reaction is generated during the atomic layer deposition (ALD) process for HfO2 grown on InSb, whereas the reaction is significantly reduced by using an Al2O3 passivation layer on InSb even during post-deposition annealing (PDA)
The electrical properties based on InSb are not as good as those based on the other III-V materials, the Al2O3 passivation layer effectively reduces the leakage current and dramatically increases the metal oxide semiconductor (MOS) capacitor performance and thermal stability in the InSb system
Summary
At 400 °C, In–Sb bonding was dissociated and diffusion through HfO2 occurred. The diffusion of indium atoms from the InSb substrate into the HfO2 increased during PDA at 400 °C. Since a 1-nm-thick Al2O3 passivation layer on the InSb substrate effectively reduced the diffusion of indium atoms, we could significantly improve the thermal stability of the capacitor. The melting point of InSb, ∼527 °C at atmospheric pressure, is insufficient for obtaining the process condition for MOSFET integration, and the bandgap of InSb, ∼0.17 eV at 293 K, is not enough to block thermal effects[7] These weak characteristics can result in defect states being generated in the MOSFET device. We examined the interfacial reaction causing interfacial traps in the HfO2/InSb system by analyzing the differences in elemental In diffusion and the chemical state at the interface between HfO2/InSb and HfO2/Al2O3/InSb. A MOS capacitor with the passivation layer of Al2O3 shows improved interface properties related to leakage current and maximum capacitance, compared with a capacitor without a passivation layer. The MOS capacitor with the passivation layer shows significantly reduced defect density
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