Copper In-Depth Distribution in Hydrogen Implanted Cz Si Wafers Subjected to Two-Step Annealing

Abstract

In this work we have studied the in-depth distribution of copper deposited on the surface of the hydrogen pre-implanted Cz Si wafers depending on the conditions of their subsequent annealing. In the standard n-type 4.5 ∙cm Cz Si wafers different numbers of radiation defects were formed by hydrogen ion implantation with an energy of 100 keV (0.9 m projected range, Rp) for different fluences (11015, 11016, or 41016 at/cm2) at room temperature. Then a copper layer 50-nm thick was deposited on the sample surface by magnetron sputtering at temperatures 250 or 300 oC with subsequent annealing for 4 h at the same temperatures. Whereupon the surface was chemically etched and the samples were annealed in vacuum during 2 h at 700 oC. The depth profiles of copper in the near-surface layer were controlled by RBS investigations both in the random and channeling modes. These experiments have shown that the copper in-depth distribution strongly depends on the implantation fluence and temperature of the low-temperature annealing: in case of copper deposition at 250 oC a relatively strong peak determined by copper on the surface is observed in RBS spectra after all the above-described steps. On the contrary, for higher temperatures of copper deposition (300 oC) a significant decrease in the intensity of this peak is observed in RBS spectra. A maximal concentration of copper at a depth of the projected range, Rp, was observed for the samples implanted with a maximal fluence (41016 at/cm2).