Room-temperature radio frequency sputtered Ta2O5: A new etch mask for bulk silicon dissolved processes

A new etch mask, namely tantalum pentoxide (Ta2O5), has been prepared for bulk silicon dissolved processes. The Ta2O5 thin films were formed at room temperature by a magnetron radio frequency sputtering technique on both sides of a double side polished 4 in. silicon wafer. Patterns were then formed on the substrate using a dielectric lift-off technique. The silicon wafer was then etched in a mixture of ethylenediamine, pyrocatechol, and water (EDP) until the exposed region of the substrate was completely removed. The thickness of the Ta2O5 thin films ranged from 100 to 700 and nm were tested as the etch masks. The etching temperature of the EDP was kept at 120 °C and the etching time was over 4 h. After etching, the surface morphology of the deposited films deteriorates with increasing etching time in EDP. The maximum roughness measured for wafers deposited with 500 nm thick Ta2O5 were 3.8±0.5 and 8.2±0.5 nm before and after EDP etch, respectively. This room-temperature technology can be used for applications in Si microelectromechanical systems and is compatible with standard indegrated circuit fabrication technology.