Etching characteristics of Si1−xGex alloy in ammoniac wet cleaning

Abstract

Etching characteristics of Si1−xGex alloys in ammoniac wet cleaning (RCA cleaning) were examined. The etching rate of Si1−xGex became larger with increasing Ge ratio (X). Temperature dependence of the etching rate was studied and the etching rate was large at high temperatures. However, no obvious difference was observed in the temperature dependence of Si1−xGex etching rate at different Ge ratio (X). A surface morhology degradation after RCA cleaning was observed at high Ge ratio (X). A stoichiometry change of Si1−xGex surface after RCA cleaning was observed by x-ray photoelectron spectroscopy (XPS). The etching rate increase and the surface morphology degradation are thought to be due to the rapid etching of Ge atoms at the top surface layer.

Etch characteristics of Si1−x Ge x films in HNO3:H2O:HF

“…As has been reported in ref. [7], etching Ge atoms diminishes the chemical bond energy of the Si 1x Ge x surface layer, which in turn accelerates the etch of Si 1x Ge x . When the HNO 3 volume increases to another critical value (it is about 35 mL), the Si can also be etched faster owing to the further enhanced oxidation ability of HNO 3 , which subsequently lowers the etch selectivity of Si 1x Ge x vs. Si.…”

“…Since the HF has been kept at 10 mL, the HNO 3 concentration dependencies may relate to the oxidation mechanism of Si 1x Ge x . In Si 1x Ge x alloys, Ge atoms are oxidized preferentially owing to the weaker Ge-Ge, Ge-Si bond energy than those of Si-Si [7,15,16]. If the HNO 3 content is low, either the Si-Si bonds or the Ge-Si and the Ge-Ge bonds are hard to be broken for oxidation, which stifles the etch rates of both Si 1x Ge x and Si.…”

“…It has been reported that such etchants as H 2 O 2 :H 2 O [4,5], HF:H 2 O 2 :CH 3 COOH [6] and NH 4 OH:H 2 O 2 [5,7] etched Si 1x Ge x more preferentially over Si. An etch rate ratio (etch selectivity) more than 100 was found for etching Si 0.7 Ge 0.3 over Si with an etchant consisting of HNO 3 :H 2 O:HF (0.5%) [8,9].…”

Temperature evolution of defects and atomic ordering in Si1−xGex islands on Si(001)

“…29 These etchants are known to selectively remove Si 1Àx Ge x over Si. 30,31 The surface morphology was then imaged by a commercial openloop AFM operated in tapping mode. We used Si tips having a radius of curvature of approximately 5 nm.…”

The effectiveness of HCl and HF cleaning of Si0.85Ge0.15 surface

“…1 Although the electrical properties and the fabrication of devices using Si 1-x Ge x have been thoroughly studied, only limited research has been carried out on their surface chemical cleaning. [3][4][5][6][7][8] Wilde et al reported the existence of hydrogen on HF cleaned Si 1-x Ge x surfaces, 9 but the nature of the surface after HF cleaning is still not clearly understood. In this study, we use synchrotron radiation photoelectron spectroscopy to examine Si 0.85 Ge 0.15 surfaces cleaned by HCl and HF solutions.…”