NEW DRY-ETCH CHEMISTRIES FOR III-V SEMICONDUCTORS

For some dry etching applications in III-V semiconductors, such as via hole formation in InP substrates, the currently used plasma chemistri es have etch rates that are too slow by up to a factor of 30. We repor t on the development of three new classes of discharge chemistries, na mely Cl2-CH4-H-2-Ar at 150-degrees-C (yielding InP etch rates of great er than 1 mum min-1 at 1 mTorr and -80 V d.c.); HBr-H-2 for selective etching of InGaAs over AlInAs; and iodine-based plasmas (HI-H-2, CH3I- H-2) that offer rapid anisotropic etching of all III-V materials at ro om temperature. In all cases electron cyclotron resonance sources (eit her multipolar or magnetic mirror) with additional r.f. biasing of the sample position are utilized to obtain low damage pattern transfer pr ocesses that generally use metal contacts on device structures as self -aligned etch masks. The temperature dependence of etch rates with the se new chemistries display non-Arrhenius behavior in the range 50-250- degrees-C and a detailed study of the phenomenon are reported. Electri cal, optical and chemical analyses of the etched surfaces show that it is possible to achieve essentially damage-free pattern transfer.