Institute of Physics and Applied Physics, Yonsei University , Seoul 120-749, Korea.
School Department of Material Science and Engineering, Sungkyunkwan University , Suwon 440-746, Korea.
ACS Appl Mater Interfaces. 2016 Mar 23;8(11):7489-98. doi: 10.1021/acsami.5b10975. Epub 2016 Mar 9.
We report on changes in the structural, interfacial, and electrical characteristics of sub-1 nm equivalent oxide thickness (EOT) HfO2 grown on InAs by atomic layer deposition. When the HfO2 film was deposited on an InAs substrate at a temperature of 300 °C, the HfO2 was in an amorphous phase with an sharp interface, an EOT of 0.9 nm, and low preexisting interfacial defect states. During post deposition annealing (PDA) at 600 °C, the HfO2 was transformed from an amorphous to a single crystalline orthorhombic phase, which minimizes the interfacial lattice mismatch below 0.8%. Accordingly, the HfO2 dielectric after the PDA had a dielectric constant of ∼24 because of the permittivity of the well-ordered orthorhombic HfO2 structure. Moreover, border traps were reduced by half than the as-grown sample due to a reduction in bulk defects in HfO2 dielectric during the PDA. However, in terms of other electrical properties, the characteristics of the PDA-treated sample were degraded compared to the as-grown sample, with EOT values of 1.0 nm and larger interfacial defect states (Dit) above 1 × 10(14) cm(-2) eV(-1). X-ray photoelectron spectroscopy data indicated that the diffusion of In atoms from the InAs substrate into the HfO2 dielectric during the PDA at 600 °C resulted in the development of substantial midgap states.
我们报告了亚 1nm 等效氧化层厚度（EOT）的 HfO2 在原子层沉积法生长于 InAs 上时的结构、界面和电性特征的变化。当 HfO2 薄膜在 300°C 的温度下沉积于 InAs 衬底上时，HfO2 呈非晶相，具有陡峭的界面、0.9nm 的 EOT 和低的预存在界面缺陷态。在 600°C 的后沉积退火（PDA）过程中，HfO2 从非晶态转变为单晶正交相，将界面晶格失配最小化至 0.8%以下。因此，PDA 后的 HfO2 电介质具有约 24 的介电常数，这是由于有序正交相 HfO2 结构的介电常数所致。此外，由于 PDA 过程中 HfO2 电介质中体缺陷的减少，边界陷阱比原始生长的样品减少了一半。然而，就其他电性特性而言，与原始生长的样品相比，PDA 处理后的样品的特性有所恶化，其 EOT 值为 1.0nm 以上，界面缺陷态（Dit）大于 1×10(14)cm(-2)eV(-1)。X 射线光电子能谱数据表明，在 600°C 的 PDA 过程中，In 原子从 InAs 衬底扩散到 HfO2 电介质中，导致大量的带隙中间态的形成。
