Clustering analysis in boron and phosphorus implanted (100) germanium by x-ray absorption spectroscopy

Recently, germanium based semiconductor device technology gained renewed interest due to new developments such as the use of high-k dielectrics for high mobility Ge MOSFETS. However, a systematic local structural investigation of clustering of dopants has been lacking in the literature. In this study, we present a detailed local structural analysis of boron and phosphorus implanted Ge wafers. We have used Ge K-edge x-ray absorption fine-structure spectroscopy (XAFS) in order to probe the local structural modifications around the Ge atom under various implantation parameters and post-implantation annealing treatments. The (100) Ge wafers were implanted and with ¹¹B ⁺ or ³¹P⁺ using energies ranging from 20 keV to 320 keV and doses of 5×10¹³ to 5×10 ¹⁶/cm². Pieces of the implanted wafers were subjected to thermal annealing at 400°C or 600°C for three hours in high purity nitrogen. Secondary ion mass spectrometry (SIMS) measurements on these wafers were used to correlate the dopant concentration profiles with the local structural information obtained from XAFS. B and P implanted Ge exhibit distinct responses to annealing. For the P implanted Ge samples annealing leads to recrystallization of Ge with increasing annealing temperature, but also an increase in Ge Debye-Waller factors, whereas B implanted Ge samples exhibit recrystallization at 400°C annealing but more randomness after 600°C annealing.