Deep reactive ion etching of III-V multilayer structures is an important issue for long wavelength vertical cavity surface emitting laser (VCSELs) where full laser structures are usually very thick. Test etchings were performed on Bragg mirror structures and monitored using laser reflectometry at 651.4 nm. In order to perform very deep etching, up to 9 μm, we designed and fabricated a special two-level mask made up of a thick nitride layer and a thin nickel layer. The etching rate is a complex function of many parameters and may change from run to run for similar structures. Therefore, it is important to have a method to control accurately the process in situ by continuously matching, experimental curves with the results of the reflectivity modeling. Here, we present a model, based on the Abelès matrix method, of the normal incidence reflectivity of a multilayer stack as a function of etch depth. Comparison between the model and the observed reflectivity variation during etching makes it possible to distinguish individual layers with very high precision.
Deep in situ dry-etch monitoring of III-V multilayer structures using laser reflectometry and reflectivity modeling
H. Moussa, R. Daneau, C. Mériadec, L. Manin, I. Sagnes, R. Raj; Deep in situ dry-etch monitoring of III-V multilayer structures using laser reflectometry and reflectivity modeling. J. Vac. Sci. Technol. A 1 May 2002; 20 (3): 748–753. https://doi.org/10.1116/1.1468652
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