In this master thesis, the goal was to devise design patterns and a fabrication processfor manufacturing a 3-D rotationally symmetric converging-diverging cold gasmicronozzle in silicon.The report explains the theory of etching and the methods involved. The work beginswith calculations and simulations of the etching processes. The chosen etch techniqueutilizes so called microloading and reactive ion etching lag effects, which essentially arephenomena where the etch rate can be adjusted by breaking up mask features intosubpatterns, and the etch depth for a given recipe and time can be made to differlocally. The subpatterns consisted of very small rectangles and triangles withalternating concentration. Five different recipes for the reactive ion etching weretried, where the coil power, platen power, pressure, temperature and time wasvaried.Etch rates could be made to differ locally depending on the concentration ofsubpatterns within the mask feature. The etch rates were also affected by the recipeparameters such as coil power, platen power, and pressure. High coil and platenpower increased the etch rate, while high pressure reduced the etch rate. The platenpower also affected the surface roughness.A solution for reducing misalignment problems in the future for the fusion bondingprocess resulted in the proposed moiré patterns that were made to showmisalignments down to 0.2 μm.Through scanning electron microscopy, the Nozzle 5_4_2 was concluded to have themost rotationally symmetric cross section at both the throat and the outlet. It hasthroat diameter of 31.1 μm with a depth of 34.2 μm and an outlet diameter of146.4 μm with a depth of 113.2 μm