MANUFACTURE OF WAVEGUIDE DIFFRACTION GRATING

摘要

PURPOSE:To obtain the difference of side etching originating from a difference in adhesion and to form a diffraction grating which has a projection and recess pattern on the side wall of a waveguide by laminating two kinds of materials and masking them alternately to an InGaAsP layer. CONSTITUTION:The InGaAsP optical waveguide layer 2 is crystal-grown on an InP substrate 1 and an SiNx film 3 is formed to form a resist diffraction grating mask 4 corresponding to the period of a desired diffraction grating. The resist mask 4 is removed after a diffraction grating pattern is transferred to the SiNx film 3, a waveguide transfer mask 6 made of resist is laminated on a diffraction grating transfer mask 5, and the waveguide transfer mask 6 made of resist is dry-etched partially. An area which is not covered with the waveguide transfer mask 6 is all removed to obtain a final etching mask. The area which is covered with SiNx is hardly side-etched right under the mask and the area covered with the resist is etched gradually according to the side etching right under the mask, so steps are formed on the side wall of the waveguide to constitute the diffraction grating.