Abstract
There is a growing interest in using high dose helium implants to alter point defect populations in silicon. Previous reports have shown that the interaction between helium and vacancies leads to the formation of cavities for medium energy (e.g., 20-100 keV) implants. However, the role of certain factors, such as the proximity of the surface, the damage created by the implant, and the effect of the implant temperature, is not well understood for low energy implants. This study explored a new regime of ultralow energy, elevated temperature implants in order to offer an insight into the effect of these parameters. Transmission electron microscopy (TEM) showed that cavity formation was avoided for 0.5 keV, 450 °C implants up to a dose of 8 × 1016 cm-2. However, extended defects in the form of {311} ribbon-like defects and stacking faults were observed. Quantitative TEM showed that the number of interstitials in these defects was less than 0.2% of the implant dose. In addition, thermal helium desorption spectrometry suggested that only 2% of the implanted He dose was retained in interstitial He and HemVn complexes. A first-order dissociation kinetic model was applied to assess desorption from HemVn, which closely matched energies predicted by density functional theory. This population of excess vacancies and excess interstitials was possibly formed because of incomplete Frenkel pair recombination. Raman spectroscopy showed that the stress from the implant was dominated by the stress from the interstitial-type defects. The evolution of the stress and defects was also explored as a function of post-implant annealing.
Original language | English |
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Article number | 165708 |
Journal | Journal of Applied Physics |
Volume | 124 |
Issue number | 16 |
DOIs | |
State | Published - Oct 28 2018 |
Funding
This work was funded through Applied Materials. The authors thank Applied Materials for performing the implants and the Research Service Centers at the University of Florida for the use of their TEM and Raman spectroscopy equipment. The THDS measurements were performed at the University of Tennessee-Knoxville and Oak Ridge National Laboratory thermal desorption system within the low-activation materials development and analysis (LAMDA) laboratory, with support from the UTK-ORNL Governor’s Chair Program and the US Department of Energy Office of Fusion Energy Sciences under Grant Nos. DE-AC05-00OR22725 and DESC0006661.