Microelectronic Engineering

High quality interfacial layer formation for Si0.75Ge0.25 (100) high-k metal gate stack

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We investigated the formation of an ultra-thin (<10 Å) and a highly stable interfacial layer (IL) using an ozonated deionized water (DIW-O3) for Si0.75Ge0.25 channel material. X-ray photoelectron spectroscopy (XPS) results confirmed the presence of mainly SiO2 with minor contributions from GeOx (GeO and GeO2) in the interfacial oxide layer. High resolution transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy (XEDS) confirms the absence of elemental Ge in the HfO2 film indicating a stable interface between the high-k and SiGe channel. An excellent electrical performance was achieved with an inversion layer thickness (Tinv) of 13.5 Å, peak hole mobility of 180 cm2 V−1.s−1 and peak interface trap defect density (Nit) of 4–4.5 × 1011 cm−2. As demonstrated, physical properties of Si0.75Ge0.25 IL is well correlated to the electrical performance highlighting the ability of DIW-O3 based IL to serve as an ideal candidate for integrating SiGe channel material in high-volume manufacturing.