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ALD deposited ZrO2 ultrathin layers on Si and Ge substrates: A multiple technique characterization

In this study, a multiple characterization technique of ultrathin ZrO2 films, deposited on high mobility substrates such as strained-Si (s-Si) and p-type Ge (p-Ge) by Atomic Layer Deposition (ALD), is presented. For reasons of comparison ZrO2 films on p-type Si (p-Si) where also studied. The stoichiometry, chemical composition and valence band electronic structure are characterized by X-ray Photoelectron Spectroscopy (XPS). For p-Si and s-Si substrates the ZrO2 valence band edge is found at 2.4 ± 0.2 eV while for the p-Ge substrate, the valence band edge is found at 2.6 ± 0.2 eV. Furthermore, Atomic Force Microscopy (AFM) measurements reveal that, all tested samples are in general smooth (0.2–0.3 nm roughness) and uniform. MOS capacitive structures were fabricated, using Al as a gate metal, and characterized electrically through CV and GV measurements. The typical behavior of a MOS structure has been revealed. Dit values, of the order of 1012 eV−1 cm−2, were calculated using Hill–Coleman method.
Highlights
• Ultra thin ZrO2 layers were grown by ALD technique on p-Si, strained Si and p-Ge substrates.
• The stoichiometry, thickness and valence band electronic structure were obtained through XPS analysis.
• AFM measurements suggest that the deposition method is successful for the formation of ultrathin ZrO2.
• C–V and G–V characteristics reveal typical MOS structure behavior, with Dit values of the order of 1012 eV−1 cm−2..
 
Fig. 1. Typical 2 × 2 μm2 AFM images obtained in non-contact mode of the ZrO2 films deposited on (a) s-Si, (b) p-Si, and (c) p-Ge (d) AFM image of the bare p-Ge substrate. Inset in (b): error signal image of the topography image where the ZrO2 “blobs” are more apparent.
 
Source: Microelectronic Engineering
 
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