Formation of Narrow, Dry‐Etched Mesas for Long Wavelength InP ‐ InGaAsP Lasers

Abstract

The reproducible fabrication of narrow (∼1.1 μm wide) mesas for buried heterostructure lasers requires development of high quality stepper lithography and anisotropic dry etching of both the etch/regrowth mask and the underlying semiconductor. Using a contrast enhancement method we demonstrate production of 1.1 μm photoresist lines with excellent uniformity (≤7% variation in width) over 2 in. φ wafers. High fidelity pattern transfer to the underlying is achieved using a low pressure (1 mTorr) electron cyclotron resonance (ECR) discharge with low additional dc bias (−75 V) on the sample. Subsequent formation of the 3.5 μm high semiconductor mesa is readily achieved using an ECR low pressure discharge (≤2 mTorr) with the sample held at ∼150°C. The semiconductor etch rate is more than an order of magnitude faster under these conditions than in conventional discharges, and there is an absence of mask narrowing.