Vapor HF Isotropic SiO2 Release Etching

For training, please contact the Tool Manager(s).

Additional Restrictions
  • No resist allowed in tool.
  • No doped oxides (PSG, BPSG) allowed.
  • Use aluminum carrier plate for pieces.

The Primaxx µEtch system is designed for low volume single wafer vapor HF etching. The system can accommodate a wafer with diameter up to 200mm.


The Primaxx HF/alcohol process employs a low pressure gas phase environment for isotropic etch removal of sacrificial silicon oxide layers to release flexures or other MEMS based devices. The process is carried out between 75-150 Torr and at temperatures between 40-60°C. Typical vertical and lateral etch rates are between 0.1-10µm/min. The process provides stiction free release with yields ->100%.

Processes Available

Fully characterized processes are available for selective etching of thermal oxide, and PECVD oxides (both silane and TEOS based) for a wide range of thicknesses. The vapor HF process is selective to metals such as Al and TiW. Other highly selective materials are Al2O3, a-Si, SiC, and LPCVD low stress nitride. Stoichiometric LPCVD silicon nitride is selective at low temperatures. PECVD nitride has a 1:1 selectivity to silicon oxide.


The key application is in the dry release of microstructures without the effect of stiction. By virtue of the reduced pressure operation, the gas phase etch process provides maximum feature penetration with its ability to remove 0.05µm thick sacrificial oxide layers under small structures. The process is exceptionally suited for complex 3D elements.