LOW-TEMPERATURE COPPER ETCHING VIA REACTIONS WITH CL2 AND PET3 UNDER ULTRAHIGH-VACUUM CONDITIONS

Reflection-absorption infrared spectroscopy, Auger electron spectroscopy (AES), temperature programmed desorption, and reactive scattering were used to investigate the adsorption and desorption behavior of PEt3 on copper and chlorinated copper surfaces under ultrahigh vacuum conditions. No reaction was observed between PEt3 and clean Cu(100) or between PEt3 and a c(2 X 2)-Cl overlayer. At temperatures above 320 K, PEt3 reacted rapidly with a heavily chlorinated copper surface (10 000 L exposure of Cl2 at 300 K). Subsequent examination of the substrate by AES showed removal of chlorine and presumably copper. The remaining chlorine corresponded roughly to 0.5 monolayer coverage. This is consistent with reactive scattering, infrared and AES experiments carried out on thin chlorinated layers (8 L Cl2 exposure), where essentially no reaction of PEt3 with the surface was observed. The reaction between PEt3 and a heavily chlorinated Cu(100) surface yields both ClCu(PEt3)2 and Cl2PEt3. These data are consistent with the etching of copper under ultrahigh vacuum conditions at low temperatures by reaction with Cl2 and PEt3 to form CuCl(PEt3)2.