Room-Temperature Inductively Coupled Plasma Etching of InP Using Cl₂N₂ and Cl₂/CH₄/H₂

We optimize the room-temperature etching of InP using Cl₂N₂ and Cl₂/CH₄/H₂ inductively coupled plasma reactive ions. A design of experiment is used in the optimization. The results, in terms of etch rate, surface roughness and etched profile, are presented. These Cl₂-based recipes do not require substrate heating and thus can be more cost effectively and widely applied. The Cl₂/CH₄/H₂ process is able to give a higher etch rate (about 850nm/min) and cleaner surface with less polymer formation compared to the conventional CH₄/H₂ process. The Cl₂/N₂ process produces even higher etch rate (as high as 2μm/min), but rougher surface with slight sidewall undercut. The Cl₂/N₂ process also has no polymer formation due to the absence of methane gas. Both the processes give very good selectivity to the silicon dioxide (SiO₂) etch mask. The selectivity of InP to the oxide mask (up to 55:1) for the Cl₂/N₂ process is one of the highest reported so far. The etched structures possess reasonably good sidewall verticality and surface quality comparable to that obtained under elevated temperature condition (>200°C).