Uniform formation of a quarter-micron period diffraction grating on a 2-inch InP wafer using reactive beam etching

Uniform formation of a 250-nm period diffraction grating on a 2-inch InP wafer was demonstrated using a Br₂-N₂ mixed gas reactive beam etching method. The electrically isolated configuration of the wafer on an etching holder is essential for obtaining rectangular shaped groove gratings. Distribution of secondary electrons generated on the holder is considered to be the dominating cause of the etching efficiency. By using a cover plate in front of the wafer, uniform distribution of the secondary electrons and uniform etching are achieved, The use of low gas pressure conditions was shown to be effective in the formation of gratings deeper than 1 μm. A waveguide Bragg filter made using the dry etching process and regrowth process is demonstrated as an example of an application for the grating device