Germanium Redistribution Phenomena in the Synthesis of SiGe Layers

Abstract

A unique germanium redistribution phenomenon occurs in the synthesis of SiGe by⁷⁴Ge⁺, ion implantation. A number of silicon samples were implanted with⁷⁴Ge⁺ ion using a range of substrate temperatures (R.T. to 600°C) with different germanium fluences (1.5 × 10¹⁶ cm⁻² to 4 × 101⁶ cm⁻²) and implantation energies (100keV - 180KeV). Samples were germanium profiled using Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS).The experimental results show that the peak range of the germanium implant increases progressively above 150°C and a shift of 40nm in the peak germanium range was measured for a sample implanted at 600°C. The ‘hot’ implants have an extended tail profile contrary to the Debye model for root-mean-square deviations of the lattice atoms from their equilibrium sites which should ideally contribute to dechanneling. The data suggest strongly that dynamic annealing related diffusion (DARD) processes exist, whereby mobile non-equilibrium point defects influence diffusion to take place at the elevated implantation temperature. The SIMS spectra of samples implanted with high Ge fluences at elevated temperature show “uphill” diffusion.