1. Localized thinning for strain concentration in suspended germanium membranes and optical method for precise thickness measurement
- Author
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Xavier Vidal, C. M. Sotomayor Torres, Miquel Garriga, Elizabeth A. Carter, Juan Sebastián Reparaz, Joffre Gutiérrez, Masahiro Yoshimoto, Alejandro R. Goñi, Pablo O. Vaccaro, Maria Isabel Alonso, D. Peró, Peter A. Lay, and Markus R. Wagner
- Subjects
Materials science ,Fabrication ,General Physics and Astronomy ,chemistry.chemical_element ,Germanium ,02 engineering and technology ,Substrate (electronics) ,01 natural sciences ,Uniaxial tensile strain ,symbols.namesake ,Strain concentration ,Etching (microfabrication) ,0103 physical sciences ,Localized thinning ,ddc:530 ,Composite material ,010302 applied physics ,Reflectivity measurements ,Fabrication strategies ,Asynchronous optical samplings ,021001 nanoscience & nanotechnology ,lcsh:QC1-999 ,Suspended membranes ,Membrane ,chemistry ,Characterization methods ,symbols ,0210 nano-technology ,Layer (electronics) ,lcsh:Physics ,Raman scattering ,Molecular beam epitaxy - Abstract
We deposited Ge layers on (001) Si substrates by molecular beam epitaxy and used them to fabricate suspended membranes with high uniaxial tensile strain. We demonstrate a CMOS-compatible fabrication strategy to increase strain concentration and to eliminate the Ge buffer layer near the Ge/Si hetero-interface deposited at low temperature. This is achieved by a two-steps patterning and selective etching process. First, a bridge and neck shape is patterned in the Ge membrane, then the neck is thinned from both top and bottom sides. Uniaxial tensile strain values higher than 3% were measured by Raman scattering in a Ge membrane of 76 nm thickness. For the challenging thickness measurement on micrometer-size membranes suspended far away from the substrate a characterization method based on pump-and-probe reflectivity measurements was applied, using an asynchronous optical sampling technique.
- Published
- 2018
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