| 摘要 |
PROBLEM TO BE SOLVED: To produce an optical waveguide having high dimensional accuracy and good perpendicularity in the cross section without decreasing the etching rate by using CHF3 and C2 F6 as an etching gas. SOLUTION: When an oxide film is subjected to dry etching, a substrate 18 is disposed on a lower electrode 3 between the upper and lower electrodes parallel to each other. An annular member 19 comprising almost the same material as the substrate 18 to be etched is arranged to surround the substrate 18. The upper face of the substrate 18 is pressed by a clamp 20 comprising almost the same material as the substrate 18, while the back surface of the substrate is held in an The gas atmosphere. The lower electrode 3 is chilled by a coolant, and CHF3 and C2 H6 are used as an etching gas. Namely, by adding C2 F6 etching gas which easily causes side etching, the side faces of the core are etched to prevent formation of a trapezoid cross section. Thus, the substrate is etched with high dimensional accuracy of the core and good perpendicularity in the cross section without decreasing the etching rate. |
