SiGe/Si microtubes fabricated on a silicon-on-insulator substrate

Abstract

We fabricated SiGe/Si free-standing micro-objects on a silicon-on-insulator (SOI) substrate using the SiO2 sacrificial layer. SiGe/Si strained films were grown by molecular beam epitaxy on SOI substrates. The films were released from the substrate by selective etching of the SiO2 layer. The released films rolled up due to the elastic strain in the SiGe layer. Microtubes and microspirals with a diameter of about 40 μm were obtained.

SiGe/Si "Micro-Origami" Epitaxial MEMS Device on SOI Substrate

“…To form the curved hinge structure, we removed the top Si layer and the upper SiGe layer using wet etching processes followed by lithography. With the lower three layers, the structure became the same as the micro-tube structure [3]. Since the thickness of the exposed top (originally middle) Si layer is larger than the bottom Si layer, the hinge bends in the direction shown in Fig.…”

“…After processing the SiGe/Si heteroepitaxial layer, the BOX layer was etched by 5% HF solution for release. To obtain a sufficient hinge curvature, the released structure was dipped into ammonia solution for further etching of the bottom Si layers [3].…”

Intrinsic stress, mismatch strain, and self-assembly during deposition of thin films subjected to an externally applied force

“…The plate bent out-of-plane after the sacrificial layer was removed. They also allowed a SiGe/Si bilayer to curl up into tubes and spirals by removing a SiO2 layer [9]. The previously mentioned studies rotated a structure about an axis in the plane.…”

“…The analysis was based on a lamination theory in which the mismatch strain could vary across the thickness of each layer. Thus, Ni et al provided a systematic way of designing the structures made by researchers in references [1][2][3][4][5][6][7][8][9][10]. However, these previous studies did not include the effects of externally applied loads during deposition.…”

Insitu Observation of the Formation Dynamics of Nanohelices

“…[1][2][3] These strained materials, when released, scroll and fold in specific patterns and shapes depending on the underlying, prebuilt strain. [1][2][3] These strained materials, when released, scroll and fold in specific patterns and shapes depending on the underlying, prebuilt strain.…”