Advanced silicon etching

Advanced Silicon Etching is a deep reactive-ion etching technique to etch deep and high aspect ratio structures in silicon. ASE was created by in 1994 in the UK. STS has continued to develop this process with faster etch rates. STS developed and first implemented the switched process, originally invented by Dr. Larmer in Bosch, Stuttgart. ASE consists in combining the faster etch rates achieved in an isotropic Si etch with a deposition or passivation process by alternating the two process steps. This approach achieves the fastest etch rates while maintaining the ability to etch anisotropically, typically vertically in Microelectromechanical Systems applications.
The ASE HRM claims to be an improvement on previous generations of ICP design, now incorporating a decoupled plasma source. The decoupled source generates high-density plasma which is allowed to diffuse into a separate process chamber. Using a specialized chamber design, the excess ions are reduced, leaving a uniform distribution of fluorine free-radicals at a higher density than that available from the conventional ICP sources. The higher fluorine free-radical density facilitates increased etch rates, typically over three times the etch rates achieved with the original process.