Uniform planarization technique for the realization of a twin-guide membrane laser

The InP Membrane on Silicon (IMOS) generic technology promises high index contrast photonic integrated circuits. To make this a reality fabrication of an electrically pumped twin-guide laser is pursued. In this paper, one of the bottle-necks for the processing is discussed, the planarization step and subsequent etch-back. Benzocyclobutene (BCB) is used to planarize SOA structures before contacting. Complete curing of BCB at 280oC creates uniformity issues during etch-back. To mitigate this, a partial cure at 180oC before the etch-back and a complete cure afterwards is performed. Experiments show repeatability and reproducibility. Good uniformity after etch-back is found.