Formation of Long Wavelength InP Laser MESAS

Abstract

ABSTRACTNarrow (1 μm), deep (3.5 μm) laser mesas have been formed on 2”φ InP wafers using stepper lithography and dry etching techniques for both dielectric and semiconductor patterning. Contrast enhancement techniques produce excellent edge acuity and vertical sidewalls on the initial photoresist lines. Pattern transfer to the underlying SiO2 regrowth mask is achieved by ECR SF6/Ar dry etching at 1 mTorr and –100V, conditions which also retain the verticality of the mesa. The semiconductor is etched using an ECR Cl2/CH4/H2/Ar discharge at 0.3 mTorr and –80V, with the sample held at ∼ 150°C. The etch rate under these conditions is ∼1 μm/min, with a selectivity of ≥10:1 for the semiconductor over the dielectric mask. The smooth etched surface and low degree of damage make this process ideal for epitaxial regrowth. The uniformity of each process step is also acceptable (≤7%). Comparison of the elevated temperature Cl2/CH4/H2/Ar mixture with the more conventional room temperature CH4/H2 plasma chemistry will be given.