Figure 4.

Fabrication process for a rolled up SiNx microtube: (a) deposition of sacrificial layer and compressively strained LF layer, followed by deposition of tensile strained HF-layer; (b) formation of rectangular mesa (optional) deposition of 100 nm PECVD SiO_x anchor, and either released from (c) both sides (process #1) or (d) one side (process #2). In both processes, the initial pad dimensions determine the final geometry. (f) Microtube diameter is determined by both LF and HF layer thickness. The deriving mathematics was previously described.⁴²