Freestanding SiGe/Si/Cr and SiGe/Si/SixNy/Cr microtubes

We report on hybrid microtubes and rings fabricated from rolled-up strained metal-semiconductor SiGe/Si/Cr and metal-insulator-semiconductor SiGe/Si/SixNy/Cr films. For making suspended microtubes, a method of directional rolling of the patterned films by anisotropic underetching of silicon substrate was introduced. It is shown quantitatively that Cr and SixNy layers are highly strained, the tensile stress being sufficient to cause the rolling-up of the hybrid films into microtubes of preset diameter. The proposed controllable and reproducible technology is promising for fabricating cylindrical-shaped microcapacitors, induction coils, transistors, and building blocks of microelectromechanical devices. (C) 2004 American Institute of Physics.