FOCUSED ION BEAM (FIB) FABRICATION OF ORIFICES FOR LEAK DETECTION APPLICATION

Nowadays helium permeation leaks are the most diffused leaks in the lowest flow range, but its flow rate is temperature dependent. On the contrary, orifice leaks has a low coefficient temperature, but they have a size (about 1 µm) that limits their applicability in the lowest flow range. The Focused Ion Beam is used in widespread fields, both technological and scientific, from nano-technology to semiconductor and material science applications. In the last years a class of Dual Beam workstations, combining a FIB column with a Scanning Electron Microscope (SEM), appeared on the market making easier to treat materials at nano-scale with precise metrology. By means of FIB it is now possible to produce orifices with a diameter on the nanoscale that allow to have flow rates, with 1 atm of pressure differential, comparable to the ranges obtained with permeation leaks. In this work we present a method to produce orifices having a diameter at nanometer scale. The orifices can be used for any gas, including mixtures, and can change continuously the flow rate simply varying the inlet pressure. The paper will present several orifices produced on different materials like silicon nitride, silicon, and metal foils. All membranes have been installed on a copper gasket mountable on NW16 Conflat® flange and tested as calibrated leaks.