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

Abstract

MeV ion implantation has been recently employed in the field of CMOS (complementary metal oxide semiconductor) retrograde well engineering. The issue on MeV ion induced damage is critical especially in forming a buried layer below the well. MeV 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 Rp (projected range) region and grown upwards to the surface during annealing. According to cross-sectional examination of etch pit density, they were generated and propagated between 700 degrees C and 800 degrees C. They shrunk or changed into long, elongated dislocation loops at higher temperatures of above 900 degrees C. SIMS (secondary ion mass spectroscopy) analyses and two-step-annealing (700 degrees C/3 similar to 6 hrs.-->900 degrees C/1 hr) results indicate that interstitial oxygens impede shrinkage of existed rod-like defects at higher temperatures of above 900 degrees C.