The damage of reactive ion etching to shallow junctions is an important consideration in advanced technology.In this paper, the damage incurred during contact etch is studied, with emphasis on those defects responsible for junction leakage of shallow junctions.Shallow p+/n and n+/p junctions have been prepared with depths of 160 nm.Junction leakage measurements have been made for various amounts of silicon loss up to within 20 nm of the junctions by using a CHF3 + CO2 plasma.The degree of chemical and structural damage has been characterized by using photoluminescence, SIMS, and spreading carrier profiling.

The leakage current density was found to depend strongly on contact area and increase rapidly with junction etch depth after the etched surface has extended to within 80 nm of the junction boundary.The concentration and depth of damage increases with increasing plasma exposure until saturation.Etching induced defects are observed in photoluminescence, and one such defect is identified as a carbon interstitialcy.Enhanced diffusion effects were observed for both chemical contamination from the etch gas and the junction dopants.The spatial distribution of the chemical and structural damage has been found to correlate with the junction leakages.The annealing behavior of damage has also been investigated.