Deep dry etching process development for photonic crystals in InP-based planar waveguides

Abstract

Chlorine-based inductively coupled plasma etching processes are investigated for the purpose of etching twodimensional photonic crystals in InP-based materials. Etch rates up to 3.7 m/min and selectivity's to the SiN mask up to 19 are reported. For the removal of indiumchloride etch products both the application of elevated temperatures and high ion energy's are investigated. The reactor pressure is an important parameter, as it determines the supply of reactive chlorine. It is shown, that N 2 passivates feature sidewalls during etching, improving the anisotropy. Ions that impact onto the sidewalls, either directly or after scattering with the SiN-mask or hole interior, cause sidewall etching. Highly directional ion bombardment and vertical sidewalls in the SiN-mask are therefore crucial for successful etching of fine high aspect ratio structures.

Photonic Crystal Structures for Photovoltaic Applications

“…Generally, two types of such crystals can be distinguished [34,35]: photonic crystals of the "hole" type (Figure 3a), consisting of cylinders with a low refractive index embedded in a medium with a high refractive index [36][37][38][39], and the "rod" type (Figure 3b), consisting of rods with a high refractive index surrounded by a medium with a low refractive index [35,[40][41][42][43][44][45]. Both holes and rods can be arranged differently to create different 2D crystal lattices.…”

2D InP photonic crystal fabrication process development

“…Djoudi et al 11 first obtained a aspect ratio as high as 14 for a hole diameter varying from 200 nm to 240 nm. Afterwards, Van der Heijden 12 and Carlstrom et al 13 have fabricated hole type photonic crystal using ICP at 250 degree with a Cl 2 +O 2 gas mixture. Although the depth and steepness are significant, the root square roughness (rms) value of internal sidewall of these deep holes were not reported.…”

Optical gain medium incorporation into semiconductor optomechanical cavities

“…In our laboratory, we use the solution with 6 % concentration in MIBK (Methyl Isobutyl Ketone), with which one may get 85 to 180 nm thick films; the minimal feature size is 6nm -which limits the beam speed, since a very small beam step size is necessary during the writing. We are specially interested in its dry etching resistance, eliminating the need of multiple fabrication steps for hard mask deposition -usually a SiO 2 or SiN x film is deposited, a lithography based on organic resist is performed and this soft mask is transfered to the film under it by etching [123][124][125]. Another positive feature from HSQ is its easy removal with HF (Hydrofluoric Acid), as any silica based film, in contrast to organic cleaning process for polymeric resists, which may damage the III-V materials.…”