A tantalum pentoxide (Ta2O5) etch mask process has been developed in the fabrication of silicon V grooves for precision positioning of optical fibers. The relationship between the Ta2O5 etch mask undercutting and the etching temperature of a mixture of ethylenediamine, pyrocatechol, and water (EDP) was studied. The Ta2O5 etch mask with a thickness of 500 nm was deposited by radio-frequency magnetron sputtering at room temperature on both sides of a 4 in. (100) Si substrate. Desired patterns were formed on the substrate using a dielectric lift-off technique. Etching temperatures of EDP ranging from 90 to 120 degreesC have been tested for the process. The undercut was found to decrease with the increasing etching temperature of EDP. At the etching temperature of 120 degreesC, an undercut of 1.61 +/- 131 mum using the Ta2O5 etch mask was achieved.