Etching patterns on the micro‐ and nanoscale

Dry etching is widely used for realizing micro‐ and nanostructured devices in various materials. Here, theavailable dry etching techniques and their capabilities at DTU‐Danchip are presented. What sets the dry etching apart from the traditional wet etching in which a chemical agent dissolved in a liquid reacts with material from the substrate is the ability to fine‐tune the etch process. In wet processing the removal of material generally occurs indiscriminately of direction in the substrate ‐ hence in all directions. This puts a strong limitation on what may be achieved in terms of designs, materials and depths. With the dry etchtools available in the cleanroom at DTU‐Danchip, the etching of a great variety of materials may be tunedvery precisely from a purely chemical and isotropic etch to a purely physical and anisotropic etch.The dry etching of silicon is the most flexible and well‐established process that enables the users of our lab to realize devices on any scale in the sub 100 nm to the sub 1 mm range. The silicon compound refractive lenses (see left figure) for focusing hard X‐rays from a synchrotron source are examples of etch processes with extreme specifications. In order to focus the X‐ray beam down to a spot size of some 100 nm, the sidewalls of the cavities etched down to 300 μm into a silicon wafer must be perfectly straight and normal to the surface and have minimum roughness.The range of possible applications of the silicon etches is greatly extended if combined with electroplating and polymer injection molding. High precision patterns of, for instance microfluidic devices, are etched intosilicon which is then electroplated with nickel that will serve as a stamp in the polymer injection molding tool where thousands of devices may be replicated. In addition to silicon and its derived materials such as oxides, nitrides or quartz, a lot of materials may bedry etched. The list includes III‐V materials that possess properties essential to photonic devices and polymers. A large number of metals and metal oxides may also be etched. In the ion milling tool we can etch basically any material – although at a somewhat limited depth. The ion beam that sputters off material may be tilted and devices such as blazed gratings (see right figure) may be produced.