In situ cleaning of InGaAs surfaces prior to low contact resistance metallization

In this work, we studied the pretreatment of InGaAs layers by employing Ar- and He-based direct plasmas and NH3, H2, NF3/NH3 remote plasmas. All the remote plasmas involved in this study were inadequate to remove the InGaAs native oxides. Moreover, for NF3/NH3 exposed samples, we noticed the addition of undesirable In–F and Ga–F bonds. Concerning Ar and He direct plasmas, investigations exhibited that both seem to be efficient for removing arsenic oxides whereas the elimination of indium oxides is more effective with Ar plasma. We also studied the addition of hydrogen into He direct plasma and we demonstrated that increasing the H2 content leads to decreasing the removal of arsenic oxides. The impact on indium oxides is also notable as we observed a reducing effect of hydrogen on indium and the emergence of In–In type bonds. Finally, whatever the plasma pretreatment, no degradation of surface morphology and roughness was observed by AFM. The RMS values obtained after surface treatments are similar with the ones acquired for reference samples.

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