Investigate on the Mechanism of HfO(2)/Si(0.7)Ge(0.3) Interface Passivation Based on Low-Temperature Ozone Oxidation and Si-Cap Methods

The interface passivation of the HfO(2)/Si(0.7)Ge(0.3) stack is systematically investigated based on low-temperature ozone oxidation and Si-cap methods. Compared with the Al(2)O(3)/Si(0.7)Ge(0.3) stack, the dispersive feature and interface state density (D(it)) of the HfO(2)/Si(0.7)Ge(0.3) stack MOS (Metal-Oxide-Semiconductor) capacitor under ozone direct oxidation (pre-O sample) increases obviously. This is because the tiny amounts of GeO(x) in the formed interlayer (IL) oxide layer are more likely to diffuse into HfO(2) and cause the HfO(2)/Si(0.7)Ge(0.3) interface to deteriorate. Moreover, a post-HfO(2)-deposition (post-O) ozone indirect oxidation is proposed for the HfO(2)/Si(0.7)Ge(0.3) stack; it is found that compared with pre-O sample, the D(it) of the post-O sample decreases by about 50% due to less GeO(x) available in the IL layer. This is because the amount of oxygen atoms reaching the interface of HfO(2)/Si(0.7)Ge(0.3) decreases and the thickness of IL in the post-O sample also decreases. To further reduce the D(it) of the HfO(2)/Si(0.7)Ge(0.3) interface, a Si-cap passivation with the optimal thickness of 1 nm is developed and an excellent HfO(2)/Si(0.7)Ge(0.3) interface with D(it) of 1.53 × 10(11) eV(−1)cm(−2) @ E−E(v) = 0.36 eV is attained. After detailed analysis of the chemical structure of the HfO(2)/IL/Si-cap/Si(0.7)Ge(0.3) using X-ray photoelectron spectroscopy (XPS), it is confirmed that the excellent HfO(2)/Si(0.7)Ge(0.3) interface is realized by preventing the formation of Hf-silicate/Hf-germanate and Si oxide originating from the reaction between HfO(2) and Si(0.7)Ge(0.3) substrate.