5.6-nm p ⁺/n junction formation for sub-0.05-μm PMOSFETs by using low-energy B ₁₀H ₁₄ ion implantation

Decaborane (B ₁₀H ₁₄) cluster ions were implanted into n-Si(100) substrates to fabricate shallow p ⁺/n junctions. Implant energies of 2 keV, 5 keV, and 20 keV, equivalent to implant energies of the monomer boron ion of 174 eV, 435 eV, and 1.74 keV, respectively, were used at dosages of 1 × 10 ¹² /cm ² and 1 × 10 ¹³ /cm ². The implanted samples were then subjected to activation annealing at 800°C, 900°C, and 1000°C for 10 s. By using secondary ion mass spectrometry (SIMS) depth profiles, we determined that the depth of the shallow junction (D _s) at a dosage of 1 × 10 ¹³ /cm ² was in the range 12 nm - 45 nm after annealing at 1000°C. D _s and transient enhanced diffusion (TED) were greatly reduced at implant energies lower than 5 keV, but thermal diffusion (TD) smoothly decreased, In particular, TED was suppressed in the p ⁺/n junction implanted at 2 keV and a dosage of 1 × 10 ¹³ /cm ², and the formation of only a 5.6-nm ultra-shallow junction was identified, This kind of extreme suppression of D _s is thought to result from the formation of well-localized damage with few interstitial defects, which act as a sinks, due to very low-energy cluster ion implantation near the surface region. The p ⁺/n junction exhibited a leakage current density of 1.8 × 10 ^-12 A/μm ² at -2 V.