Structural and electrical characterization of Si(100) implanted with P + and Si + ions along the [100] channelling direction

Abstract

Double implantations of 100 keV Si + and P + ions with a total dose of 1×10 15 cm −2 have been performed in Si(100) along the [100] channelling direction. Buried amorphous layers of thickness 130 nm were formed beneath a crystalline top layer 60 nm thick. The phosphorus peak concentration in the buried amorphous layer varied between 2×10 18 cm −3 and 6×10 19 cm −3. An enhancement of regrowth velocity by a factor of 1.2–1.45 due to phosphorus has been observed. After solid phase epitaxial regrowth of the buried layer an “interface” remains at the depth at which the two amorphous/crystalline interfaces meet. Both planar channelling analysis between the {100} planes as well as cross-sectional transmission electron microscopy show that dislocation loops are present after full recrystallization at the “buried interface”. The size of the dislocation loops becomes smaller in the presence of phosphorus. The thermal stability of the buried interface during high temperature annealing depends on the size of the dislocation loops. It is largest in the absence of phosphorus. Nucleation of dislocation loops by excess phosphorus and silicon atoms occurs at the interface as shown by transmission electron microscopy. The number of phosphorus atoms involved in the nucleation of dislocation loops at the buried interface saturates at about 1×10 14 cm −2. Formation of the buried interface after recrystallization can be prevented by a successive 75 keV, 1×10 15 Si + cm −2 random implant to amorphize the silicon top layer completely. After two-step annealing at 550 °C for 2 h then at 900 °C for 1 h the number of Hall charge carriers amounts to 90% of the implanted phorphorus dose.