Etching issues in etching compound and Si-based device fabrication

Summary form only given. Ion-induced damage is an important issue in III-V and Si-Ge devices. The principal cause of damage is the introduction of traps and point defects by ions penetrating into the semiconductor. At the low ion energies used in modem process technology (100 eV say) the bulk of the ions remain on or within a few nm of surfaces. However, some ions channel along the III direction and so penetrate into the semiconductor to a depth of 30 to 50 nm. In HEMT's with f/sub T/ greater than 100 GHz, the active current carrying layer is only 30 to 50 nm below the surface. In compound semiconductor it is usually impossible to anneal such damage away. An analytic model of this channelling has been developed and its accuracy checked by measuring the penetration of ions produced by a very low energy implantation. An important finding is that while atomic ions (e.g. Cl/sup +/) can channel and so cause damage molecular ions (e.g. Cl/sub 2//sup +/) do not. This can be used to predict processes that will be suitable for low damage.