Deep Reactive Ion Etch (DRIE)

Reactive ion etching is a further development of reactive ion etching and was developed by Robert Bosch GmbH in the early 1990s. Reactive ion etching is a further development of reactive ion etching and was originally developed in the early 1990s by Robert Bosch GmbH. Therefore, the process is also called "Bosch process". It was further developed in the following years and made commercially available. This improved process is marketed together with the plant technology under the name "Advanced Silicon Etching" (ASE). The DRIE process is a highly anisotropic dry etching process for the production of silicon microstructures. The method is iterative and based on the use of a passivation layer which, in conjunction with a superimposed DC voltage, causes anisotropy in the etching process. The goal is to etch as anisotropically perpendicular to the substrate surface.


Selectivity, anisotropy and etch rate are adjustable by gases and process parameters (RF power, pressure, gas flow, substrate cooling, etc.). Anisotropy is achieved by sidewall passivation.


Step 1: Passivation with polymers (C4F8)
Step 2: Opening the polymer by directional particle bombardment (SF6)
Step 3: Isotropic etching of the silicon on the etching ground

Application areas:

  • Sensor technology
  • Actuator
  • Micro-optics
  • Microfluidics


  • SPTS Pegasus, high-rate etcher is operated on the ASE
  • Only SF6 and C4F8 in process
  • Connected gases: SF6, C4F8, O2, Ar
  • RF coupling through a coil (ICP)
  • Helium backside cooling
  • Clamping by electrostatic chuck
  • Edge protection possible

Performance Data

Aspect ratio (Depth:Width) up to 30:1
Flank angle 90° +/- 2°
Etchrate up to 10µm
Maximum etching depth Through wafer etch possible (725µm)