Boron doping of silicon by plasma source ion implantation

Abstract

We have performed an extensive analysis of the structural and electrical characteristics of 150 and 200 mm Si wafers boron doped by low-energy (−0.5 to −5 kV) plasma source ion implantation (PSII) from a BF 3 plasma and subsequent rapid thermal annealing. The formation of shallow junctions (60 nm or less) required for 0.18 μm device geometries has been verified by secondary ion mass spectrometry measurements and electrical characterization. Rutherford backscattering spectrometry and high resolution electron microscopy analyses have shown a thin (≤5 nm) amorphous region in the as-implanted silicon; no evidence of dislocations or other extended defects has been observed. After annealing, the implanted silicon appears to be perfectly crystalline. Good doping uniformity across a wafer and good wafer-to-wafer repeatability have been observed in the PSII process. Excellent device characteristics (threshold voltage rolloffs, junction leakage, etc.) have been obtained from MOSFET structures fabricated using this doping technology. All results suggest that boron doping of silicon by PSII results in materials and device characteristics that are suitable for advanced device fabrication.