Advanced silicon etching (ASE) is a deep reactive-ion etching (DRIE) technique to rapidly etch deep and high aspect ratio structures in silicon.ASE was pioneered by Surface Technology Systems Plc. (STS) in 1994 in the UK. STS has continued to develop this process with even greater etch rates while maintaining side wall roughness and selectivity.STS developed the switched process originally invented by Dr. Larmer at Bosch, Stuttgart.ASE consists in combining the fast etch rates achieved in an isotropic Si etch (usually making use of an SF6 plasma) with a deposition or passivation process (usually utilising a C4F8 plasma condensation process) by alternating the two process steps. This approach achieves the fastest etch rates while maintaining the ability to etch anisotropically, typically ve