Atom Ejection Studies for Sputtering of Semiconductors

Abstract

Atom-ejection patterns resulting from the sputtering of semiconductor single crystals have been examined. The annealing temperature Ta (here defined as the minimum target temperature for which single-crystal spot patterns are observed) previously reported for Ge, Si, InSb, and InAs, has now been determined for GaAs and CdTe. For target temperatures below Ta damage remains frozen in and the deposit indicates an amorphous or polycrystalline surface. For GaAs one finds Ta∼130°C for Ar+ and Ne+ ion bombardment; for CdTe no spot patterns are observed up to 510°C where the target begins to evaporate. No clear correlation of Ta with other physical properties is noticeable. We had previously reported that spot patterns persist even for T<Ta if the bombarding-ion energy is less than some critical energy. We have now demonstrated that no such critical energy exists. The 〈111〉 and 〈1̄1̄1̄〉 deposits resulting from sputtering of InAs and GaAs (110) surfaces were studied. The 〈1̄1̄1̄〉 spot [the normal to the (1̄1̄1̄) face, which terminates with a triply bonded In or Ga atom] is generally slightly thicker (by∼10%) than the 〈111〉 spot. For GaAs the 〈1̄1̄1̄〉 spot is slightly richer in Ga and the 〈111〉 spot is slightly richer in As. No compositional differences were noted for the deposits from InAs.