Passivation of Ge surface treated with trimethylaluminum and investigation of electrical properties of HfTiO/Ge gate stacks

In the current work, in situ surface passivation Ge substrate by using trimethylaluminum (TMA) prior to HfTiO films deposition and electrical properties of HfTiO/Ge gate stacks have been investigated by X-ray photoelectron spectroscopy (XPS) and electrical measurements systematically. Based on analysis from XPS measurements, it has been confirmed that the interfacial layer of HfTiO/Ge gate stack has been suppressed effectively after 20 half-ALD cycles TMA pretreatment. Electrical properties of metal-oxide-semiconductor (MOS) capacitor based on HfTiO gate dielectrics have shown that the MOS capacitor with 20 cycles TMA cleaning exhibits the lowest interface state density (∼7.56 eV−1 cm−2) and the smallest leakage current (∼2.67 × 10−5 A/cm2). Correspondingly, the leakage current conduction mechanisms for MOS capacitor device with 20 cycles TMA cleaning also have been discussed in detail.