A study on the defects in the fabrication of CMOS retrograde well including a buried layer using MeV ion implantation

MeV ion implantation has been recently employed in the field of CMOS (complementary metal oxide semiconductor) retrograde well engineering. An issue on MeV ion induced damage is critical especially in forming a buried layer below the well. MeV B implanted buried layers were observed to show greatly improved characteristics of latchup suppression. Junction leakage current, however, showed a critical behavior as a function of ion dose. The rod-like defects were observed to be responsible for the leakage current. Rod-like defects were generated near the R_p (projected range) region and grown upward to the surface during annealing. According to cross sectional examination of etch pit density, they were generated and propagated between 700°C and 800°C. They shrink or change into long, elongated dislocation loops at higher temperatures above 900°C. Results of SIMS (secondary ion mass spectroscopy) analyses and two-step-annealing (700°C/3~6 hrs.→900°C/1 hr.) indicate that interstitial oxygens impede shrinkage of existing rod-like defects at higher temperatures above 900°C