The Fabrication of High Precision Nozzles by the Anisotropic Etching of (100) Silicon

Abstract

Arrays of nozzles of uniform size (~-~25 • 25 ~m ~) and spacing (~-~0.3 mm) suitable for high quality and high speed ink-jet printing have been fabricated by the anisotropic etchi~ng of holes through (I00) Si wafers using conventional Si-processing techniques. The etchant used is a mixture of pyrocatechol, ethylene diamine, and water. The nozzles are well-defined truncated, square pyramidal cavities bounded by 4 convergent {111} planes. The square orifice, side Wo, is given by Wo ~ WB-~/2 tsi, where WB is the side of the square base and tsi the wafer thickness. Successful fabrication of these silicon micro-structures requires the application of well-controlled patterning and etching processes and the selection of a uniform, defect-free, accurately oriented single crystal substrate. Arrays of nozzles of uniform size and spacing are required to generate drops of ink with uniform characteristics for high speed and high resolution ink-jet printing using binary, deflected, electrostatically charged ink jets (1-5). In ink-jet printing, fine jets of conductive ink are formed by forcing the pressurized ink through an array of nozzles; the jets break up into uniform streams of droplets by vibrating the nozzle array at a fixed frequency by means of a piezoelectric * Electrochemical Society Active Member.