FORMATION OF THIN-FILM WAVEGUIDE ELEMENT

• Main Author: AOKI MASAKANE
• Format: Patent
• Language: English
• Published: 19.01.1996
• Edition: 6
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

PURPOSE:To form an optically flat reflection end face by lessening the striation at the perpendicular end face of a waveguide. CONSTITUTION:The thin-film optical waveguide is constituted by laminating a core layer 20 consisting of SiON by a plasma CVD method and a clad layer 22 consisting of SiON likewise by a plasma CVD method in this order via a buffer layer 21 consisting of thermally oxidized SiO2 on a semiconductor Si substrate 1. Next, a mask layer 5 consisting of a photoresist is formed to desired patterns on this clad layer 22 and, thereafter, this photoresist is etched down to the buffer layer 21 by using this mask layer 5 as a mask, and a gaseous mixture composed of gaseous fluorocarbon (for example, CHF3) and oxygen as an etchant by a reactive etching (RIE) method which is one of anisotropic dry etching, by which the end faces 3 of the waveguides nearly perpendicular to the main surface of the substrate 1 are formed and exposed. Next, the entire part of the element inclusive of the end faces 3 of the waveguide is immersed into a buffered hydrofluoric acid soln. or dilute hydrofluoric acid soln. which is an isotropic chemical etching soln., by which the ruggedness of the striation 4 is flattened and lessened.