Activation of dopant in silicon by ion implantation under heating sample at 200 °C

Abstract

Activation and carrier generation are reported in the case of phosphorus implantation with a dose of 2.0 × 10¹⁵ cm⁻² at 70 keV to crystalline silicon substrates under heating ranging from 200 to 500 °C. The analysis of the optical reflectivity spectra of implanted surfaces revealed that the effective amorphized thickness was low of 2.9 nm in the case of 200 °C-phosphorus implantation, while it was large of 140 nm for implantation at room temperature. The carrier density par unit area increased from 6.9 × 10¹³ to 4.8 × 10¹⁴ cm⁻² and the photo-induced minority carrier effective lifetime increased from 2.2 × 10⁻⁶ to 1.6 × 10⁻⁴ s as the implantation temperature increased from 200 to 500 °C. Defect reduction with 1.3 MPa H₂O vapor heating at 250 °C for 3 h increased the carrier density par unit area of the 200 °C-phosphorus-implanted sample to 2.7 × 10¹⁴ cm⁻². The rectified characteristics were obtained by current–voltage measurement in the case of phosphorus implantation to p-type silicon substrate. Photovoltaic effect was also observed. These results show that the ion implantation under low temperature heating has a capability of p–n junction formation.