Epitaxial growth of a silicon capping layer to mitigate roughness after the selective chemical etching of Si1-xGex (original) (raw)
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1997
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The surface contamination was known to affect the roughening during anisotropic e<tching. We studied the role of the initial surface states of silicon after different cleaning treatments (hydrogen-saturated, fluorine-saturated) over the way the ekhing proceeds. We investigated three types of ultimate-cleaning solutions after the standard RCA treatment: HF:H20 1:lO (followed by DI water rinsing and drying), HF:C2H,OH 1:lO (dried without any further rinsing), and 10% HCI in HF:H20 1: I (also dried without rinsing). Since atomic scale roughness variations, as well as contamination affect the gate oxide integrity, we have correlated these results with electrical parameters extracted from C-V characteristics.
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Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2009
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2010
The effects of H 2 gas evolution during the etching of silicon surfaces by aqueous ammonium fluoride ͑NH 4 F͒ solutions were investigated by scanning tunneling microscopy, atomic force microscopy, optical microscopy, and noncontact profilometry. If H 2 bubbles, a reaction product, were removed from the etching surface or if their coalescence was suppressed, near-atomically flat surfaces were produced. Otherwise, the etched surface developed significant roughening on many length scales with several characteristic morphological features, including nested, nearly-concentric circular etch pillars, circular etch pits, and faceted micropits. Mechanisms for the production of all three types of features are proposed. Chemical and physical means of suppressing bubble-induced surface roughening are presented. These results explain the conventional wisdom that aqueous fluoride etchants roughen Si͑100͒ surfaces, in part by promoting the formation of Si͕111͖ microfacets. Although some conditions promote the formation of a high density of ͕111͖-faceted micropits ͑areal densities of 30%-50% were observed͒, microfacet formation is not inherent to the atomic-scale reactions. Instead, the microfacets are a direct result of gas evolution during the etching reaction.
X-ray diffraction analysis of the silicon (111) surface during alkaline etching
Surface Science, 2011
We present a surface X-ray diffraction determination of the silicon (111)-liquid interface structure during alkaline etching. Preparation of an atomically smooth surface was realized by an in-situ procedure using an aqueous NH 4 F solution devoid of oxygen. Using diluted aqueous potassium hydroxide (KOH) and ammonium fluoride (NH 4 F) etchant, we have observed that the crystal surface is hydrogen terminated and is not reconstructed at open circuit potential. In addition, a partial liquid ordering of two water layers on top of the crystal surface was found, indicating a weak interaction with the hydrophobic, hydrogen terminated surface. We have followed in-situ the development of the oxide layer by a birth and spread mechanism during anodic passivation of the silicon surface.
Anisotropic selective etching between SiGe and Si
Japanese Journal of Applied Physics, 2018
In Si/SiGe dual-channel FinFETs, it is necessary to simultaneously control the etched amounts of SiGe and Si. However, the SiGe etch rate is higher than the Si etch rate in not only halogen plasmas but also physical sputtering. In this study, we found that hydrogen plasma selectively etches Si over SiGe. The result shows that the selectivity of Si over SiGe can be up to 38 with increasing Ge concentration in SiGe. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) results indicate that hydrogen selectively bonds with Si rather than with Ge in SiGe. During the etching, hydrogen-induced Si surface segregation is also observed. It is also observed that the difference in etched amount between SiGe and Si can be controlled from positive to negative values even in Si/SiGe dual-channel fin patterning while maintaining the vertical profiles. Furthermore, no plasma-induced lattice damage was observed by transmission electron microscopy for both Si and SiGe fin sidewalls.