Defect characterization of n-type Si1−xGex after 1.0 kev helium-ion etching

Abstract

SiGe heterostructures with their associated geometries and properties promise a novel generation of Si-based devices. Surface processing and, in particular, dry or plasma etching of semiconductors is a key technology for producing optoelectronic integrated circuits and high speed electronic devices. We have used deep-level transient spectroscopy (DLTS) in an investigation of the electronic properties of defects introduced in n-Si 1 −xGex (x = 0.00 to 0.25) during 1 keV helium-ion etching (fluence = 1 × 1012 cm²) prior to the deposition of gold Schottky barrier diodes (SBDs). Six electron defects (EHel-EHe6) were detected after this processing stage. The defects detected after etching are compared to those introduced by 5.4 MeV alpha-particle (α-) irradiation and, also, radio frequency (rf) sputter-deposition of Au SBDs on material from the same wafer. Four of the electron defects (EHel, EHe2, EHe4, and EHe6) are detected in Si. The remaining two defects (EHe3 and EHe5) are only detected in material containing germanium. It was noted that defects introduced during the He-ion etch process have the same DLTS “signatures” as defects after the sputter deposition process, but none were the same as those introduced during the α-particle irradiation. The influence of increased Ge content on DLTS peak shape and positions is also illustrated and discussed.