High-aspect-ratio inductively coupled plasma etching of InP using SiH4/Cl2: Avoiding the effect of electrode coverplate material

A new SiH4/Cl2 chemistry is proposed for the high-aspect-ratio etching of InP-based heterostructures. Anisotropic etching is obtained through the deposition of a SiOx passivation layer on the etched sidewalls. SiH4 has been chosen as a single precursor for both Si and H species that are necessary to promote the passivation process. Previously developed Cl2/H2- or HBr-based chemistries for anisotropic etching of laser waveguides or vertical microcavities require a silicon wafer below the InP samples in order to assist the passivation mechanism. In contrast, the authors show that a SiOx passivation can be achieved and maintained almost independent of the nature of the wafer surface when SiH4 is added. This is of practical importance for the processing of III-V wafers having the same size as the electrode or for III-V heterogeneous integration when III-V dies bonded onto a 200/300 mm diameter wafer have to be etched. Smooth, notch-free, anisotropic etching of InGa(Al)As/InP heterostructures is demonstrated. ...