Total dose measurement for ion implantation using laser ablation ICP-MS

Abstract

Laser ablation coupled with a quadrupole based ICP-MS (LA-ICP-MS) has been used for quantitative analysis of the total dopant dose implanted in crystalline silicon wafers. Four commonly used dopant ions in the semiconductor industry, namely 11B+, 75As+, 121Sb+ and 31P+, were studied in this work. The penetration depths and vertical profiles of these implanted ions in silicon were simulated using `stopping and range of ions in matter' (SRIM) and utilized to help select the laser sampling parameters. The ICP-MS conditions were optimized to obtain the best signal-to-noise (S/N) and signal-to-background (S/B) ratios using the implanted silicon wafers. The linear analytical calibration curves have been constructed from the standardized wafers with both <100> and <111> crystal orientations. Multiple prime wafers with known dopant ion concentrations implanted at 80 KeV have been used to assess the analytical precision and accuracy of the technique. It is our hope that this method can eventually be utilized to calibrate ion implanters in different fabrications and correlate the total dose levels employed in different fabrication processes for very large scale integration (VLSI) and ultra-large scale integration (ULSI) devices.