A 50 nm-wide 5 μm-deep copper vertical gap formation method by a gap-narrowing post-process with Supercritical Fluid Deposition for Pirani gauge operating over atmospheric pressure

This paper describes a method to narrow trenches by metal layer growth on sidewalls with Supercritical Fluid Deposition (SCFD). Trenches are fabricated by Deep Reactive Ion Etching (DRIE) of silicon followed by copper layer deposition with SCFD. Trenches of 440 nm-wide and 5 μm-deep were eventually narrowed to 50 nm. As an application, a Pirani gauge that utilizes such 50 nm gaps to achieve operation over atmospheric pressure was fabricated and operation up to at least 0.116 MPa (1.2 bar) was confirmed. The estimated upper limit of the operation range is 1 MPa (10 bar).