Phosphorus Followed by Hydrogen Two-Step Ion Implantation Used for Forming Low Resistivity Doped Silicon at 300°C

Abstract

We report formation of low resistivity n-type doped silicon region at 300°C by the method of two-step ion implantation. Phosphorus ions with a dose of 2×10¹⁴ cm⁻² at 70 keV followed by hydrogen ions with 1×10¹⁶ cm⁻² at 8 keV were implanted at RT to the both surfaces of single crystalline silicon substrates. Post heating at 300°C for 90 min decreased the sheet resistivity to 417 Ω/sq. The activation ratio was estimated as 75% under the assumption of electron mobility of 50 cm²/Vs in the doped region. Moreover, the minority carrier effective lifetime (τeff) was also increased to 253 μs. This indicates a low density of surface recombination defect states of 6.4×10¹⁰ cm⁻². In contrast, a high sheet resistivity of 8×10⁴ Ω/sq and a low τeff of 64 μs resulted from a single phosphorus ion implantation with 2×10¹⁴ cm⁻² at 70 keV followed by 300°C heating for 90 min. The hydrogen ion implantation probably decreased the silicon bonding energy to easily move phosphorus atoms in the silicon lattice sites at 300°C and passivated the doped region by terminating silicon dangling bonds.