Formation of hollow glass microcylinders of silica

The formation of hollow microcylinders, starting from a thin film of sputtered glass, is reported. To begin, a three-inch silicon wafer was coated with 5 µm of SiO2. An RF sputtering system was then used to deposit 1.7 µm film of a multi-component glass. The sputter target was an erbium-doped lanthanum sodium silicate glass, normally used for optical amplification and filtering. Ridge waveguides with rectangular cross-sections (~ 6 µm x 1 µm) were obtained by partially wet-etching die sputtered glass film. The waveguides were then annealed in a thermal oxidation furnace. When heated above the glass transition temperature, the rectangular ridges were re-shaped into hollow cylinders with a diameter of approximately 9 mm. The hollow microcylinders remained structurally intact over distances of up to 1 cm. Similar results were observed with structures fabricated from three different sputter deposition runs, indicating that the process was repeatable. Early results investigating the cause for this transformation will be presented. Attempts to launch light and fluid in this structure will also be discussed. These microcylinders may find application as microchannels for gas/fluid transport, grooves for fiber alignment and microlenses.